REVISION 3

Which ion has the most shells that contain electrons?

• Al³⁺

• Be²⁺

• N^3–

• S^2–

The table gives data about four substances.

Which substance could be an ionic compound?

• A

• B

• C

• D

Answer explanation

Properties of ionic compound is it has high melting point and can conduct electricity when aqueous.

The table shows the electron structures of four elements.

Which pair of atoms will form a covalent substance?

• two atoms of W

• two atoms of X

• an atom of W and an atom of X

• an atom of Y and an atom of Z

Answer explanation

Covalent is formed between two non - metals. W is a non - metal (six valency electrons means it belongs to group VI).

How does a magnesium atom form a bond with an oxygen atom?

• by giving one pair of electrons to the oxygen atom

• by sharing one pair of electrons, both electrons provided by the magnesium atom

• by sharing two pairs of electrons, both pairs provided by the oxygen atom

• by sharing two pairs of electrons, each atom donating one pair of electrons

Answer explanation

Magnesium is a metal so it gives two valency electrons to oxygen. Oxygen is a non - metal so it gains two valency electrons from magnesium.

Which of the following contains the same number of electrons as an atom of neon?

• Cl^–

• Li

• Li⁺

• O^2–

Answer explanation

O^2– means oxygen gains two valency electrons, it has electronic 2,8 which is the same as electronic structure of Neon.

What is the most suitable way of investigating the different food colourings in some drinks?

• crystallisation

• filtration

• fractional distillation

• paper chromatography

Which statement about an atom of X is correct?

• It is in Group III of the Periodic Table.

• It is in Group VII of the Periodic Table.

• The total number of protons and electrons is 6.

• The total number of protons and neutrons is 10.

Answer explanation

Nucleon number = 7

Proton number = 3

Electron number = 3

Neutron number = 7 - 3 = 4

Electronic structure = 2, 1

Group number = 1

How many electrons are shared in the covalent bonding of a methane molecule?

• 2

• 4

• 6

• 8

Answer explanation

Formula of methane is CH₄ as shown in the diagram.

Which statement about the alkali metals is true?

• they form covalent bonds with Group VII elements

• they form oxides on reacting with water

• their melting points decrease on descending Group I

• their reactivities decrease on descending Group I

Answer explanation

Down the group, melting point decreases as shown in the picture.

Which gas is present in the light bulb?

• argon

• krypton

• nitrogen

• oxygen

Answer explanation

Argon does not react with filament/tungsten of bulbs even at high temperature as it is an inert gas (unreactive gas).