CIE iGCSE Co-ordinated Sciences-C8.1 Arrangement of elements- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-C8.1 Arrangement of elements – Study Notes
CIE iGCSE Co-ordinated Sciences-C8.1 Arrangement of elements – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
The Periodic Table
The Periodic Table is an arrangement of all known chemical elements in a systematic way based on their properties and atomic structure.
Key Features:
- Elements are arranged in periods (horizontal rows) and groups (vertical columns).
- Each element is placed in order of increasing proton number or atomic number.
- Elements in the same group have similar chemical properties because they have the same number of valence electrons.
- Elements in the same period show a gradual change in properties across the row.
Example
Why is sodium placed in Group 1 and Period 3 of the Periodic Table?
▶️Answer/Explanation
Sodium has an atomic number of 11 and one valence electron.
It is placed in Period 3 because it has three electron shells, and in Group 1 because it has one valence electron, giving it similar chemical properties to other Group 1 elements.
Example
Explain why chlorine is in Group 17 and Period 3.
▶️Answer/Explanation
Chlorine has an atomic number of 17 and seven valence electrons.
It is placed in Period 3 because it has three electron shells, and in Group 17 because it has seven valence electrons, which gives it similar chemical properties to other halogens.
Change from Metallic to Non-Metallic Character Across a Period
As you move across a period in the Periodic Table from left to right:
- Elements gradually change from metals to non-metals.
- Metallic character decreases. Metals on the left are typically shiny, malleable, ductile, and good conductors of heat and electricity.
- Non-metallic character increases. Non-metals on the right are usually brittle, dull, and poor conductors of heat and electricity.
- This trend is due to the increasing nuclear charge (more protons in the nucleus) and decreasing atomic radius, which makes it harder for atoms to lose electrons and easier to gain electrons.
Example
Compare the metallic character of sodium (Na) and chlorine (Cl).
▶️Answer/Explanation
Sodium is a metal with one valence electron and easily loses it to form positive ions.
Chlorine is a non-metal with seven valence electrons and tends to gain an electron to form negative ions.
Therefore, metallic character decreases from sodium to chlorine across the period.
Example
Explain why aluminum (Al) is more metallic than phosphorus (P).
▶️Answer/Explanation
Aluminium is a metal that loses three electrons easily, showing metallic character.
Phosphorus is a non-metal that tends to gain three electrons to form ions.
As we move across Period 3, the metallic character decreases, so Al is more metallic than P.
Chemical Similarities of Elements in the Same Group
Elements in the same group of the Periodic Table have similar chemical properties because they have the same number of electrons in their outermost shell (valence electrons).
Key Points:
- The number of valence electrons determines how an element reacts chemically.
- Elements in the same group react similarly with other substances, such as acids, water, and oxygen.
- For example, all Group 1 elements have one valence electron and all Group 17 elements have seven valence electrons.
Example
Explain why lithium, sodium, and potassium show similar chemical reactions.
▶️Answer/Explanation
All three elements are in Group 1 and have one valence electron in their outermost shell.
This single electron is easily lost, making them highly reactive metals that react vigorously with water and acids to form hydroxides and hydrogen gas.
Therefore, their similar electronic configuration leads to similar chemical properties.
Example
Why do chlorine, bromine, and iodine have similar chemical properties?
▶️Answer/Explanation
All three elements are in Group 17 and have seven valence electrons.
They tend to gain one electron to form negative ions (halide ions), showing similar reactions with metals to form salts.
Their similar valence electron configuration explains the chemical similarity among halogens.
Trends in Groups
Within a group of the Periodic Table, elements show predictable trends in physical and chemical properties due to their similar electronic configurations. These trends can be identified when given information about elements.
Key Trends:
- Atomic radius: Increases down a group because each element has an additional electron shell.
- Ionization energy: Decreases down a group as outer electrons are further from the nucleus and easier to remove.
- Reactivity: For metals (e.g., Group 1), reactivity increases down the group. For non-metals (e.g., Group 17), reactivity decreases down the group.
- Melting and boiling points: Can increase or decrease depending on the group (e.g., Group 1 metals have decreasing melting points down the group, while Group 17 halogens have increasing melting points down the group).
Example
Given that lithium, sodium, and potassium react with water to produce hydrogen, predict the trend in reactivity.
▶️Answer/Explanation
All three are Group 1 metals with one valence electron.
Reactivity increases down the group because the outer electron is further from the nucleus and more easily lost.
Therefore, potassium is more reactive than sodium, which is more reactive than lithium.
Example
Given that chlorine, bromine, and iodine react with potassium to form salts, predict the trend in reactivity.
▶️Answer/Explanation
All three are Group 17 halogens with seven valence electrons.
Reactivity decreases down the group because atoms are larger, and the nucleus has less attraction for an additional electron.
Therefore, chlorine is more reactive than bromine, which is more reactive than iodine.