CIE iGCSE Co-Ordinated Science C8.1 Arrangement of elements Exam Style Questions Paper 4
Question
Fig. 11.1 shows an outline of the Periodic Table.
(a) Draw a line to link each element to its correct description.
Use each description only once.
▶️Answer/Explanation
He – an element with an electronic structure of 2
Al – an element in Group 3 and Period 3
Ar – an element with 8 electrons in its outer shell
(b) Argon is a gas used in lamps. Explain why.
▶️Answer/Explanation
Argon is a noble gas, which means it is chemically inert and does not react with other substances. This makes it ideal for use in lamps, as it prevents the filament from oxidizing and burning out quickly.
(c) The nucleus of a carbon atom contains six protons. State the charge on a proton.
▶️Answer/Explanation
The charge on a proton is +1.
(d) Potassium metal reacts with the non-metal bromine to form potassium bromide. Potassium bromide is an ionic compound. Describe how metallic and non-metallic elements form ionic bonds.
▶️Answer/Explanation
Metallic elements lose electrons to form positively charged ions (cations), while non-metallic elements gain electrons to form negatively charged ions (anions). These oppositely charged ions are held together by strong electrostatic forces, forming an ionic bond. In the case of potassium bromide, potassium (K) loses one electron to form K⁺, and bromine (Br) gains one electron to form Br⁻, resulting in the ionic compound KBr.
(e) The electronic structure of carbon is 2.4. The electronic structure of oxygen is 2.6. The atoms in a molecule of carbon dioxide, CO₂, are held together by covalent bonds. Draw the dot-and-cross diagram to show the bonding in carbon dioxide. You only need to include the outer shell electrons.
▶️Answer/Explanation
In the dot-and-cross diagram for CO₂:
Carbon has 4 outer electrons and forms double bonds with each oxygen atom.
Each oxygen atom has 6 outer electrons and shares 2 electrons with carbon to complete its octet.
The structure is linear, with carbon in the center and oxygen atoms on either side.
