Pre AP Chemistry -2.2C Periodic Trends- MCQ Exam Style Questions -New Syllabus 2025-2026

Pre AP Chemistry -2.2C Periodic Trends- MCQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Chemistry -2.2C Periodic Trends- MCQ Exam Style Questions – Pre AP Chemistry – per latest Pre AP Chemistry Syllabus.

Pre AP Chemistry – MCQ Exam Style Questions- All Topics

Question

Which option describes the electronic configurations of three different elements from the same group of the Periodic Table?

A) 2 2,2 2,8,8,2
B) 2 2,8 2,8,2
C) 2,1 2,8,1 2,8,8,1
D) 2,1 2,2 2,3

▶️ Answer/Explanation

Solution

Ans: C

Elements in the same group have the same number of valence electrons. Let’s analyze each option:

Option A: Shows configurations with 2, 2, and 2 valence electrons respectively – but the second element (2,2) is in Group 2 while the third (2,8,8,2) is in Group 2 but the first (2) is helium (Group 18).
Option B: Shows configurations with 2, 8, and 2 valence electrons – different numbers, so not same group.
Option C: All configurations end with 1 valence electron (2,1; 2,8,1; 2,8,8,1) – these are all Group 1 elements (alkali metals).
Option D: Shows 1, 2, and 3 valence electrons respectively – different groups.

Only option C shows three elements all with 1 valence electron, meaning they’re in the same group (Group 1).

Question

Which statement about the Periodic Table is correct?

A) All the metals in the Periodic Table are transition elements.
B) The halogens are elements in Group I of the Periodic Table.
C) The elements become more metallic across a period from Group I to Group VII.
D) The Periodic Table can be used to predict the properties of the elements.

▶️ Answer/Explanation

Solution

Ans: D

Let’s evaluate each option:

A: Incorrect – There are many metals (like alkali and alkaline earth metals) that aren’t transition elements.
B: Incorrect – Halogens are in Group VII, not Group I.
C: Incorrect – Elements become less metallic (more non-metallic) across a period from left to right.
D: Correct – The Periodic Table organizes elements by atomic number and shows periodic trends in properties, allowing predictions about element behavior.

The Periodic Table’s main purpose is to show periodic trends and allow prediction of element properties based on position.

Question

Which compound is made from elements that are all in the same period?

A) Al₂(SO₄)₃
B) C₂H₅OH
C) LiNO₃
D) Na₃AlF₆

▶️ Answer/Explanation

Solution

Ans: C

To solve this, we need to check which compound contains elements all from the same period (row) in the Periodic Table.

Option A: Al (Period 3), S (Period 3), O (Period 2) – different periods
Option B: C (Period 2), H (Period 1), O (Period 2) – different periods
Option C: Li (Period 2), N (Period 2), O (Period 2) – all same period
Option D: Na (Period 3), Al (Period 3), F (Period 2) – different periods

Only LiNO₃ contains elements that are all in Period 2.

Question

Part of the Periodic Table is shown.

Which element is a metal?

▶️ Answer/Explanation

Solution

Ans: A

From the periodic table shown in the question (not visible in text), we can deduce:

1. Metals are typically found on the left side and middle of the periodic table.

2. Non-metals are found on the right side.

3. The question indicates that element A is a metal, which would be positioned in the metal region of the periodic table.

Therefore, the correct answer is option A.

Question

Four mixtures each contain a halogen and an aqueous sodium halide. Which row describes what happens in the mixtures shown?

▶️ Answer/Explanation

Solution

Ans: C

1. Halogen Reactivity Series:
F > Cl > Br > I (decreasing oxidizing power)
A halogen can displace any halide below it in the series 2. Key Observations:
• Cl₂ + 2NaBr → 2NaCl + Br₂ (orange solution)
• Br₂ + 2NaI → 2NaBr + I₂ (brown solution)
• No reaction when less reactive halogen is added 3. Color Changes:
• Chlorine water: Pale yellow-green
• Bromine solution: Orange
• Iodine solution: Brown 4. Why Option C:
Correctly identifies both successful displacement reactions where the added halogen is more reactive than the halide present

Question

Which statements about elements in the Periodic Table are correct?

Elements in the same group have the same number of electrons in their outer shell.
Elements in the same period have the same number of occupied electron shells.
The elements are arranged in order of their atomic mass.
Every period contains eight elements.

A 1 and 2
B 1 and 3
C 2 and 4
D 3 and 4

▶️ Answer/Explanation

Solution

Ans: A

Analysis of each statement about Periodic Table organization:

Statement	Evaluation	Explanation
1	Correct	Group number = valence electrons (main group elements)
2	Correct	Period number = principal quantum number (n) of outermost shell
3	Incorrect	Arranged by atomic number (protons), not mass
4	Incorrect	Period lengths vary (2, 8, 8, 18, 18, 32, 32 elements)

Key periodic trends:

Groups (vertical):
- Same valence electron configuration
- Similar chemical properties
Periods (horizontal):
- Same number of electron shells
- Properties change progressively

Therefore, only statements 1 and 2 are correct, making option A the right answer.

Question

Which statements describe changes that occur from left to right across a period of the Periodic Table?
1 The atomic number of the elements increases.
2 The metallic character of the elements decreases.
3 The physical state of the elements changes from gas to solid.
A 2 only

B 1 and 2

C 1 and 3

D 2 and 3

▶️ Answer/Explanation

Solution

Ans: B (1 and 2)

Periodic trends analysis:

Statement 1 (Correct):
- Atomic number increases by 1 across each period
- This is the fundamental organization principle of the Periodic Table
Statement 2 (Correct):
- Metallic character decreases left to right
- Elements change from metals → metalloids → nonmetals
- Due to increasing electronegativity and ionization energy
Statement 3 (Incorrect):
- Physical state doesn’t follow a consistent gas→solid pattern
- Example: Period 2 starts with solid Li, ends with gas Ne
- Physical state depends on specific elements, not periodic position

Therefore, only statements 1 and 2 correctly describe periodic trends.

Question

Which row about elements in the Periodic Table is correct?

▶️ Answer/Explanation

Solution

Ans: A

Analysis of each periodic table property:

Option	Evaluation	Scientific Basis
A	Correct	Metals are malleable (can be hammered into sheets) Non-metals form acidic oxides (e.g., CO₂, SO₂) Group 0 elements are unreactive noble gases
B	Incorrect	Non-metals are poor conductors, not good
C	Incorrect	Metals form basic oxides, not acidic
D	Incorrect	Group 0 elements are unreactive, not very reactive

Key periodic table facts:

Metal properties:
- Malleable and ductile
- Form basic oxides (e.g., Na₂O, CaO)
- Good conductors of heat/electricity
Non-metal properties:
- Brittle when solid
- Form acidic oxides (e.g., SO₃, P₄O₁₀)
- Poor conductors (except graphite)
Noble gases:
- Group 0/18 elements
- Extremely low reactivity (full outer electron shells)
- Monatomic gases at room temperature

The image shows Option A as the only completely correct description of these periodic table properties.

Question

Which statement about the Periodic Table is correct?

A Elements with the highest atomic number in each period are metallic.
B Elements with the lowest group numbers are non-metals.
C Elements with similar chemical properties are placed in groups.
D Elements with similar physical properties are placed in periods.

▶️ Answer/Explanation

Solution

Ans: C

1. Periodic Table Organization:
– Groups (vertical columns) contain elements with similar chemical properties due to identical valence electrons
– Periods (horizontal rows) show trends in physical properties
2. Evaluating Options:
– A: Incorrect – Noble gases (Group 18) are non-metallic
– B: Incorrect – Groups 1-2 contain highly reactive metals
– C: Correct – Fundamental principle of periodic table organization
– D: Incorrect – Physical properties change gradually across periods

Question

The positions of four elements in the Periodic Table are shown.
Which element is a gas that displaces iodine from sodium iodide?

▶️ Answer/Explanation

Solution

Ans: C (Chlorine)

Key analysis:

Displacement reaction requirement:
Cl₂(g) + 2NaI(aq) → 2NaCl(aq) + I₂(aq)
- Only chlorine gas (Cl₂) can displace iodine from NaI
- This demonstrates chlorine’s higher reactivity in Group 17
Periodic Table positions:
- Chlorine is above iodine in Group 17 (halogens)
- Higher halogens can displace lower ones from their salts
Why other options are incorrect:
- A: Too reactive (alkali metal)
- B: Noble gas – doesn’t react
- D: Less reactive than iodine (can’t displace it)

Key points:

Chlorine is the only gas among the options
It’s more electronegative than iodine (can oxidize I^– to I₂)
The reaction shows a classic halogen displacement

Therefore, Option C (chlorine) is the correct answer.

Question

The elements in Period 3 of the Periodic Table are shown.

Which statements about the elements in Period 3 are correct?

1. Na, Mg and Al are metals.
2. S, Cl and Ar are non-metals.
3. Si, P and S are metals.

A. 1 and 2 only

B. 1 and 3 only

C. 2 and 3 only

D. 1, 2 and 3

▶️ Answer/Explanation

Solution

Ans: A

Analysis of Period 3 elements:

Element Group	Classification	Notes
Na, Mg, Al	Metals	Conduct electricity, malleable
Si	Metalloid	Semiconductor properties
P, S, Cl, Ar	Non-metals	Poor conductors, brittle

Evaluation of statements:

Correct: Na, Mg, Al are all metals
Correct: S, Cl, Ar are non-metals
Incorrect: Si is a metalloid, P and S are non-metals

Therefore, only statements 1 and 2 are correct, making option A the right answer.

Question

Part of the Periodic Table is shown.
Which element forms an acidic oxide?

▶️ Answer/Explanation

Solution

Ans: B

Periodic Trends Analysis:

Element Identification:
- B is carbon (C) – Group 14 nonmetal
- Forms CO₂ and CO (both acidic oxides)
Acidic Oxide Characteristics:
- React with water to form acids (CO₂ + H₂O → H₂CO₃)
- React with bases to form salts
- Typical of nonmetal oxides
Other Elements:
- A (Al) – Forms amphoteric oxide (Al₂O₃)
- C (Mg) – Forms basic oxide (MgO)
- D (Na) – Forms strongly basic oxide (Na₂O)

Chemical Evidence:

CO₂ turns limewater milky (acidic property test)
Forms carbonic acid in water (pH ≈ 4)
Reacts with NaOH: CO₂ + 2NaOH → Na₂CO₃ + H₂O

Therefore, only B (carbon) forms a definitively acidic oxide among the options.

Question

Which statements describe the Periodic Table?

1 The elements are arranged in order of their nucleon number.
2 The elements are arranged in order of their proton number.
3 It is used to predict the properties of elements.
A 1 and 3 B 1 only C 2 and 3 D 2 only

▶️ Answer/Explanation

Solution

Ans: C

Statement Analysis

Statement 1: “Elements arranged by nucleon number”

False – Nucleon number (mass number) is not the basis
Example: Tellurium (atomic number 52) comes before iodine (53) despite having higher mass

Statement 2: “Elements arranged by proton number”

True – Atomic number (proton count) determines position
Fundamental organizing principle since Moseley’s work (1913)

Statement 3: “Used to predict properties”

True – Periodic trends allow prediction of:
- Reactivity (e.g., Group 1 metals get more reactive down group)
- Melting points (e.g., higher for metals in middle of d-block)
- Ionization energies (periodic pattern across periods)

Option	Evaluation
A (1 and 3)	Incorrect – Statement 1 is false
B (1 only)	Incorrect – Statement 1 is false
C (2 and 3)	Correct – Both statements true
D (2 only)	Incomplete – Misses predictive power

Conclusion: The Periodic Table is arranged by proton number (atomic number) and enables property prediction through periodic trends, making Option C correct.

Question

A period of the Periodic Table is shown.

The letters are not their chemical symbols.
Which statement is correct?
A Element R does not conduct electricity.
B Elements R and Y react together to form an ionic compound.
C Element Z exists as a diatomic molecule.
D Element Z reacts with element T.

▶️ Answer/Explanation

Solution

Ans: B (Elements R and Y react together to form an ionic compound)

Periodic Table Analysis:

The elements shown represent a typical period with:

R: Alkali metal (Group 1)
S: Alkaline earth metal (Group 2)
T: Transition metal (Groups 3-12)
U: Metalloid
V: Non-metal
W: Non-metal
X: Non-metal
Y: Halogen (Group 17)
Z: Noble gas (Group 18)

Evaluation of Statements:

A: Incorrect – R (alkali metal) conducts electricity
B: Correct – Alkali metal (R) + Halogen (Y) → Ionic compound (e.g., NaCl)
C: Incorrect – Z (noble gas) exists as monatomic, not diatomic
D: Incorrect – Z (noble gas) is inert and doesn’t react with T

Chemical Explanation:

Alkali metals (R) readily lose 1 electron to form cations
Halogens (Y) readily gain 1 electron to form anions
This electron transfer creates strong ionic bonds
Example: R (Na-like) + Y (Cl-like) → RY (NaCl-like)

Why Other Options Are Wrong:

A: All metals conduct electricity
C: Only halogens/hydrogen/nitrogen/oxygen form diatomic molecules
D: Noble gases are chemically inert

Therefore, the only correct statement is B, as it correctly describes ionic compound formation between an alkali metal and a halogen.

Question

Which statement about the Periodic Table is correct?
A Most metallic elements are on the left.
B Elements in the same period have the same number of outer electrons.
C Elements on the left are usually gases.
D The relative atomic mass of the elements increases from right to left.

▶️ Answer/Explanation

Solution

Ans: A

Detailed Analysis of Each Option:

Option	Evaluation	Explanation
A	Correct	Left side contains Groups 1-2 (s-block) and transition metals (d-block) These are all metallic elements (e.g., Na, Mg, Fe) Metallicity decreases moving right across periods
B	Incorrect	Elements in the same group have same outer electrons Elements in same period have increasing outer electrons (e.g., period 2: Li(1) → Ne(8))
C	Incorrect	Left-side elements are metals (solids at room temp) Gases appear on the far right (Noble gases) and some in p-block (O₂, N₂)
D	Incorrect	Atomic mass generally increases left to right across periods Also increases top to bottom in groups Exceptions exist due to isotopes (e.g., Ar > K in period 3)

Periodic Trends Supporting Option A:

Metallic Character:
- Highest in bottom-left (Francium most metallic)
- Decreases moving up and right
Electron Configuration:
- Left-side elements readily lose electrons (metallic bonding)
- Right-side elements tend to gain electrons (non-metals)

Visual Representation:

Metallicity Trend: Metals (left) → Metalloids (diagonal) → Non-metals (right)

Therefore, the only completely correct statement is A, as it accurately describes the distribution of metallic elements in the Periodic Table.

Question

The diagram shows elements W, X, Y and Z in a section of the Periodic Table.

Which statement about the reactivity of the elements is correct?

A) X is more reactive than Y, and W is more reactive than Z.
B) X is more reactive than Y, and Z is more reactive than W.
C) Y is more reactive than X, and W is more reactive than Z.
D) Y is more reactive than X, and Z is more reactive than W.

▶️ Answer/Explanation

Solution

Ans: C

1. Element Identification:
• W: Fluorine (F) – Group 17
• X: Sodium (Na) – Group 1
• Y: Potassium (K) – Group 1
• Z: Chlorine (Cl) – Group 17 2. Reactivity Trends:
• Group 1 (Alkali Metals):
  – Reactivity increases down the group (K > Na)
  – Due to decreasing ionization energy
• Group 17 (Halogens):
  – Reactivity decreases down the group (F > Cl)
  – Due to decreasing electronegativity 3. Correct Relationships:
• Y (K) > X (Na) in reactivity
• W (F) > Z (Cl) in reactivity
Thus confirming option C 4. Experimental Evidence:
• K reacts violently with water vs Na’s vigorous reaction
• F reacts with nearly all elements vs Cl’s selective reactivity

Question

Which statement about elements in Group VIII of the Periodic Table is correct?

A. They all have a full outer shell of electrons.
B. They all react with Group I elements to form ionic compounds.
C. They are all diatomic molecules.
D. They are all liquids at room temperature.

▶️ Answer/Explanation

Solution

Ans: A

Analysis of Group VIII (Noble Gases) properties:

Option	Evaluation	Scientific Explanation
A	Correct	Noble gases have complete valence shells: He: 2 electrons (1s²) Others: 8 electrons (ns²np⁶)
B	Incorrect	Noble gases are inert and don’t readily form compounds (except Xe/Kr under extreme conditions)
C	Incorrect	Noble gases exist as monatomic (single-atom) molecules
D	Incorrect	Physical states at room temperature: He/Ne/Ar/Kr/Xe: gases Rn: radioactive gas

Key characteristics of noble gases:

Electron Configuration: Stable octet (or duplet for He)
Reactivity: Extremely low due to filled valence shells
Physical State: All gases at standard conditions
Atomicity: Monatomic molecular form

Therefore, only statement A correctly describes the defining feature of Group VIII elements – their complete outer electron shells.

Question

Which set of elements shows the change from metallic to non-metallic character across a period of the Periodic Table?

beryllium → magnesium → calcium
fluorine → bromine → iodine
oxygen → boron → lithium
sodium → silicon → chlorine

▶️ Answer/Explanation

Solution

Ans: D (sodium → silicon → chlorine)

Analysis of each option:

Option	Elements	Pattern	Evaluation
A	Be → Mg → Ca	Group 2 metals (vertical)	All metals
B	F → Br → I	Group 17 (vertical)	All nonmetals
C	O → B → Li	Reverse period	Nonmetal → metalloid → metal
D	Na → Si → Cl	Period 3 (horizontal)	Metal → metalloid → nonmetal

Only option D correctly shows the left-to-right transition across a period from metallic (Na) through metalloid (Si) to nonmetallic (Cl) character.

Question

Which pair of elements reacts together most violently?

chlorine and lithium
chlorine and potassium
iodine and lithium
iodine and potassium

▶️ Answer/Explanation

Solution

Ans: B

Analysis of reactivity trends:

Option	Reactivity Factors	Violence of Reaction
A (Cl + Li)	Li less reactive than K Cl highly reactive	Vigorous but less than B
B (Cl + K)	K most reactive alkali metal here Cl most reactive halogen here	Most violent (flames/sparks)
C (I + Li)	I least reactive halogen Li less reactive than K	Moderate reaction
D (I + K)	K highly reactive I less reactive halogen	Vigorous but less than B

Key chemical principles:

Alkali metal reactivity:
- Increases down Group 1: K > Li
- K has weaker metallic bonding (larger atomic radius)
Halogen reactivity:
- Decreases down Group 17: Cl > I
- Cl higher electronegativity than I
Reaction violence:
- 2K + Cl₂ → 2KCl (extremely exothermic)
- Produces violet flame and explosive sounds

Therefore, chlorine and potassium (B) react most violently due to the combination of the most reactive alkali metal and most reactive halogen in the options.

Question

Part of the Periodic Table is shown.

Which element is used to provide an inert atmosphere?

▶️ Answer/Explanation

Solution

Ans: C

1. Identifying the Elements:
– A: Sodium (Na) – reactive metal
– B: Chlorine (Cl) – reactive non-metal
– C: Argon (Ar) – noble gas
– D: Potassium (K) – reactive metal
2. Inert Atmosphere Requirements:
Noble gases (Group 18) are chemically inert due to complete valence shells.
3. Industrial Applications:
Argon (Ar) is commonly used in:
– Welding to prevent oxidation
– Light bulbs to prevent filament combustion
– Food packaging to prevent spoilage

Question

The elements sodium to argon form Period 3 of the Periodic Table.

Which row describes the trend across Period 3 from left to right?

▶️ Answer/Explanation

Solution

Ans: C

Key trends across Period 3 (Na to Ar):

Property	Trend	Explanation
Atomic radius	Decreases	Increasing nuclear charge pulls electrons closer
Electronegativity	Increases	Greater nuclear attraction for bonding electrons
Metallic character	Decreases	Transition from metals → metalloids → non-metals
Outer electrons	Increase (1→8)	Each element adds one more electron

Option C correctly shows:

Decreasing atomic radius
Increasing electronegativity
Decreasing metallic character

This matches all major periodic trends across Period 3.

Question

Which statement explains why elements in Group VIII of the Periodic Table are unreactive?

They are monatomic gases.
They form stable diatomic molecules.
They have a full outer shell of electrons.
They share electrons with each other.

▶️ Answer/Explanation

Solution

Ans: C

The noble gases (Group VIII) are unreactive because:

Electron Configuration:
- They possess a complete valence shell (octet for most, duet for helium)
- This stable configuration doesn’t require gaining/losing/sharing electrons
Why Other Options Are Incorrect:
- A: Monatomic nature is a consequence of their stability, not the cause
- B: Noble gases don’t form diatomic molecules (except under extreme conditions)
- D: They don’t share electrons as they’re already stable
Chemical Significance:
- Their full outer shell gives them high ionization energies and zero electronegativity
- This explains their lack of chemical reactivity under normal conditions

Thus, the fundamental reason for their unreactivity is having a full outer shell of electrons (Option C).

Question

Part of the Periodic Table is shown.
Which element forms an acidic oxide?

▶️ Answer/Explanation

Solution

Ans: C

Periodic Table Analysis:

Element Identification:
- C is sulfur (S) – Group 16 nonmetal
- Forms SO₂ and SO₃ (both acidic oxides)
Acidic Oxide Properties:
- SO₂ + H₂O → H₂SO₃ (sulfurous acid)
- SO₃ + H₂O → H₂SO₄ (sulfuric acid)
- React with bases to form sulfites/sulfates
Other Elements:
- A (Mg) – Forms basic oxide (MgO)
- B (Al) – Forms amphoteric oxide (Al₂O₃)
- D (Si) – Forms weakly acidic oxide (SiO₂)

Chemical Evidence:

Sulfur oxides turn blue litmus red
Form strong acids in water (pH < 3)
React completely with NaOH: SO₂ + 2NaOH → Na₂SO₃ + H₂O

Therefore, C (sulfur) forms the most strongly acidic oxide among the options.

Question

Which statement about trends in the Periodic Table is not correct?
A Elements in the same period have the same number of electron shells.
B The elements change from metals to non-metals from left to right.
C The number of protons in an atom of an element increases from left to right.
D The oxides of the elements change from acidic to basic from left to right.

▶️ Answer/Explanation

Solution

Ans: D

Periodic Trend Analysis

Option	Evaluation	Explanation
A	Correct	Period number = number of electron shells
B	Correct	Left: Metals (Na, Mg) → Right: Non-metals (P, S, Cl)
C	Correct	Atomic number increases left to right
D	Incorrect	Oxides change from basic to acidic, not acidic to basic

Oxide Trend Details

The correct oxide trend across a period is:

Basic oxides → Amphoteric oxides → Acidic oxides

Examples in Period 3:

Na₂O (strongly basic)
Al₂O₃ (amphoteric)
SO₃ (strongly acidic)

Conclusion: Option D reverses the actual trend of oxide character across periods. The correct statement should be: “The oxides change from basic to acidic from left to right,” making D the incorrect option.

Question

Which statement about the Periodic Table is not correct?
A It can be used to find the atomic number of an element.
B It can be used to find the physical state of an element.
C It can be used to find the symbol of an element.
D It can be used to predict the properties of an element.

▶️ Answer/Explanation

Solution

Ans: B

Analysis of Each Statement:

Option	Correctness	Explanation
A	Correct	The atomic number (proton number) is the fundamental organizing principle of the Periodic Table, appearing with each element.
B	Incorrect	The Periodic Table does not show physical states: Physical state depends on temperature and pressure (e.g., bromine is liquid at room temp while mercury is the only other liquid metal) Most periodic tables don’t indicate state at standard conditions State must be determined experimentally or from reference data
C	Correct	Element symbols are a standard feature of all Periodic Tables (e.g., Fe for iron, O for oxygen).
D	Correct	Periodic trends allow prediction of properties like reactivity, electronegativity, and bonding type based on position.

Why Option B is the Correct Answer:

Physical State Variability:
- Elements can exist in different states under different conditions (e.g., oxygen is gas at room temp but liquid at -183°C)
- No standard representation of states in the table layout
What the Periodic Table Actually Shows:
- Atomic number and mass
- Element symbols and names
- Electron configuration patterns
- Periodic trends in chemical properties

Key Exception:

While most periodic tables don’t show physical states, some educational versions might color-code states at standard temperature and pressure (STP). However, this is not a fundamental feature of the Periodic Table itself.

Therefore, B is the correct choice as it identifies the statement that is not true about the standard Periodic Table.

Question

Which element is in the same period of the Periodic Table as silicon?

Germanium
Scandium
Sodium
Strontium

▶️ Answer/Explanation

Solution

Ans: C

1. Periodic Table Position:
• Silicon (Si): Period 3, Group 14
• Sodium (Na): Period 3, Group 1 2. Why Sodium is Correct:
• Both have electrons filling the 3rd energy level
• Same principal quantum number (n=3) 3. Other Elements’ Periods:
• Germanium (Ge): Period 4 (same group as Si)
• Scandium (Sc): Period 4
• Strontium (Sr): Period 5 4. Key Characteristics of Period 3:
• Contains 8 elements (Na to Ar)
• Shows transition from metallic to nonmetallic character
• Includes important elements like Al, P, and S

Question

Iodine, I, has a lower relative atomic mass than tellurium, Te, but is placed after it in the Periodic Table.

Which statement explains why iodine is placed after tellurium in the Periodic Table?

A Iodine has fewer neutrons than tellurium.
B Iodine has fewer protons than tellurium.
C Iodine has more neutrons than tellurium.
D Iodine has more protons than tellurium.

▶️ Answer/Explanation

Solution

Ans: D

This question demonstrates the fundamental principle of Periodic Table organization:

Element	Atomic Number	Atomic Mass	Position
Tellurium (Te)	52	127.60	Before Iodine
Iodine (I)	53	126.90	After Tellurium

Key concepts:

Periodic Law: Elements are arranged by atomic number (proton count), not atomic mass
Anomalous Pair: Te (52p, 76n) vs I (53p, 74n) – I has lower mass but higher atomic number
Chemical Properties: Iodine’s 53 protons give it different chemical behavior than tellurium

Why other options are incorrect:

A: Neutron count doesn’t determine position (Te-76n, I-74n)
B: Incorrect proton comparison (I has more protons)
C: Actually, iodine has fewer neutrons

Therefore, option D correctly identifies that iodine’s higher proton count (atomic number) determines its position, despite its lower atomic mass.

Question

The Periodic Table lists all the known elements.

Elements are arranged in order of …….1……. number.

The melting points of Group I elements …….2……. down the group.

The melting points of Group VII elements …….3……. down the group.

Which words correctly complete gaps 1, 2 and 3?

▶️ Answer/Explanation

Solution

Ans: C (proton, decrease, increase)

Complete explanation:

Gap 1: proton
- Elements are arranged by increasing proton (atomic) number
- This is the fundamental organizing principle of the Periodic Table
Gap 2: decrease
- Group I (alkali metals) melting points decrease down the group
- Due to increasing atomic size weakening metallic bonds
- Example: Li (181°C) → Na (98°C) → K (64°C)
Gap 3: increase
- Group VII (halogens) melting points increase down the group
- Due to increasing van der Waals forces between larger molecules
- Example: F₂ (-220°C) → Cl₂ (-101°C) → Br₂ (-7°C)

This combination correctly describes both the organization of the Periodic Table and the contrasting trends in Groups I and VII.

Question

Which trend occurs across the period from sodium to argon?

a change from metal to non-metal
an increase in melting point
a more violent reaction with water
an increase in electrical conductivity

▶️ Answer/Explanation

Solution

Ans: A

Analysis of periodic trends from Na (Period 3 start) to Ar (Period 3 end):

Element Sequence	Classification	Key Properties
Na, Mg, Al	Metals	Good conductors, malleable, basic oxides
Si	Metalloid	Semiconductor, amphoteric oxide
P, S, Cl	Non-metals	Poor conductors, acidic oxides
Ar	Noble gas	Non-metal, inert, no oxide formation

Evaluating each option:

A (Correct):
- Clear transition: Na/Mg/Al (metals) → Si (metalloid) → P/S/Cl (non-metals) → Ar (noble gas)
- Demonstrates the metal-nonmetal transition across periods
B (Incorrect):
- Melting points: Na(98°C) → Mg(650°C) → Al(660°C) → Si(1414°C) → P(44°C) → S(115°C) → Cl(-101°C) → Ar(-189°C)
- Peaks at silicon then decreases
C (Incorrect):
- Reactivity with water decreases: Na (violent) → Mg (slow) → Al (protective oxide layer prevents reaction)
- Non-metals don’t react with water in same way
D (Incorrect):
- Conductivity decreases: Good (metals) → Moderate (Si) → Poor (non-metals) → None (Ar)

Therefore, only option A correctly describes the trend from sodium to argon.

Question

Which property of elements increases across a period of the Periodic Table?

A metallic character
B number of electron shells
C number of outer shell electrons
D tendency to form positive ions

▶️ Answer/Explanation

Solution

Ans: C

1. Periodic Trends:
Across a period (left to right):
– Outer electrons: Increase from 1 to 8 (Option C correct)
– Metallic character: Decreases (Option A wrong)
– Electron shells: Constant within a period (Option B wrong)
– Positive ion formation: Decreases (Option D wrong)
2. Electronic Configuration:
Each element adds 1 more valence electron than the previous
Example: Period 2 elements have 2nd shell e^– counts from 1 (Li) to 8 (Ne)
3. Why Others Are Incorrect:
Metallic character and positive ion tendency decrease as electronegativity increases

Question

Part of the Periodic Table is shown.
Which element is a soft solid that reacts violently with cold water?

▶️ Answer/Explanation

Solution

Ans: D (Rubidium – Rb)

Key characteristics of the correct element:

Alkali metal properties:
- Soft, silvery solids (can be cut with a knife)
- Extremely reactive with water
- Single valence electron makes them highly reactive
Violent water reaction:
2Rb(s) + 2H₂O(l) → 2RbOH(aq) + H₂(g) + heat
- Produces hydrogen gas (may ignite)
- Exothermic reaction (may cause explosion)
- Forms alkaline hydroxide solution
Periodic Table position:
- Group 1 element (alkali metals)
- Below potassium in reactivity series

Why other options are incorrect:

A: Transition metal (less reactive with water)
B: Alkaline earth metal (reacts slowly with water)
C: Halogen (non-metal, doesn’t react this way)

Therefore, Option D (Rb) is the correct answer as it shows all the described properties.

Question

In the Periodic Table, how does the metallic character of the elements vary from left to right across a period?

It decreases.
It increases.
It increases then decreases.
It stays the same.

▶️ Answer/Explanation

Solution

Ans: A

The metallic character decreases across a period due to:

Atomic Structure Changes:
- Increasing nuclear charge pulls electrons closer
- Decreasing atomic radius makes electron loss harder
Trends in Properties:
- Left side: Alkali/alkaline earth metals (strong metallic character)
- Middle: Transition metals (moderate metallic character)
- Right side: Nonmetals (no metallic character)
Why Other Options Are Incorrect:
- B: Opposite of observed trend
- C: No periodic trend shows this pattern
- D: Clearly changes across periods

Key evidence:
• Ionization energy increases left to right (harder to remove electrons)
• Electronegativity increases (greater electron attraction)
• Electrical conductivity decreases

Thus, metallic character decreases from left to right across a period (Option A).

Question

Which statement about the Periodic Table is correct?

Elements in the same period have the same number of outer electrons.
The elements on the left are usually gases.
The most metallic elements are on the left.
The relative atomic mass of the elements increases from right to left.

▶️ Answer/Explanation

Solution

Ans: C

1. Periodic Trends Analysis:
• Metallic character decreases left to right across periods and increases down groups
• Leftmost elements (Groups 1-2) are highly metallic (e.g., Na, K, Ca) 2. Why Other Options Are Incorrect:
• A: Elements in same group (not period) share outer electrons
• B: Left-side elements are mostly solids (except H gas)
• D: Atomic mass generally increases left to right 3. Metallic Properties:
• Good conductors of heat/electricity
• Malleable and ductile
• Form positive ions (lose electrons) 4. Visualizing the Trend:
Metallic character peak at bottom-left (Fr) and minimum at top-right (He)

Question

The results of three tests on a solution of compound X are shown in the table.

What is compound X?
A aluminium bromide
B aluminium chloride
C zinc bromide
D zinc chloride

▶️ Answer/Explanation

Solution

Ans: B (aluminium chloride)

Analysis of test results:

Test	Observation	Explanation
NaOH(aq)	White precipitate	AlCl₃ + 3NaOH → Al(OH)₃↓ + 3NaCl (white gelatinous ppt)
NH₃(aq)	White precipitate	AlCl₃ + 3NH₃ + 3H₂O → Al(OH)₃↓ + 3NH₄Cl
AgNO₃(aq)	White precipitate	AlCl₃ + 3AgNO₃ → 3AgCl↓ + Al(NO₃)₃ (white curdy ppt)

Key identification points:

All three tests produce white precipitates characteristic of Al³⁺ and Cl^–
Zinc compounds would give soluble complex with excess NaOH
Bromides would give cream-colored AgBr precipitate

Therefore, Option B (aluminium chloride) is the only compound that matches all test results.

Pre AP Chemistry -2.2C Periodic Trends- MCQ Exam Style Questions -New Syllabus 2025-2026