Chemistry Paper 1

What three subatomic particles make up an atom and what are their charges?

Protons (+1), Neutrons (0), and Electrons (−1).

What is the equation to calculate mass number?

Mass number = protons + neutrons.

What are isotopes?

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.

How do you determine the electronic structure of the first 20 elements?

Electrons occupy shells filling in the order 2, 8, 8, 2.

What does the group number in the periodic table indicate for Groups 1–7?

It indicates the number of electrons in the outer shell.

What type of ion do alkali metals form and what is their reactivity trend?

They form +1 ions and reactivity increases down the group.

What is the general reaction for metals reacting with water?

Metal + water → metal hydroxide + hydrogen.

What do halogens have in common and how do they react?

They have 7 outer electrons and react with metals to form ionic compounds, decreasing in reactivity down the group.

What is the nature of noble gases and their group characteristics?

They have a full outer electron shell, are very unreactive, and their boiling points increase down the group.

What is ionic bonding?

Ionic bonding occurs between a metal and a non-metal where electrons are transferred, forming oppositely charged ions.

What is a giant ionic lattice?

A structure formed by ionic compounds characterized by high melting and boiling points and strong electrostatic attractions.

When do ionic compounds conduct electricity?

They conduct electricity when molten or dissolved in water.

What type of bonding involves the sharing of electron pairs between non-metal atoms?

Covalent bonding.

What are the properties of simple molecular substances?

They have strong covalent bonds within molecules, weak intermolecular forces between molecules, low melting and boiling points, and usually do not conduct electricity.

What is an empirical formula?

The empirical formula shows the simplest whole-number ratio of atoms in a compound.

What is the general formula for calculating percentage yield in chemistry?

Percentage yield = actual yield ÷ theoretical yield × 100.

How does the pH scale determine acidity and alkalinity?

pH < 7 = acidic, pH = 7 = neutral, pH > 7 = alkaline.

What is the observation test for hydrogen gas?

A lighted splint produces a squeaky pop sound.

What happens during electrolysis at the cathode and anode?

At the cathode, positive ions gain electrons (reduction); at the anode, negative ions lose electrons (oxidation).

What is an exothermic reaction?

A reaction that transfers energy to the surroundings, causing temperature to increase.

What improvements can be made to temperature change experiments?

Use a better-insulated container, use a lid to reduce heat loss, or use a more precise thermometer.

What is the Rf value in chromatography?

Rf = distance travelled by substance ÷ distance travelled by solvent.

Why do we use a pencil line in paper chromatography?

Because pencil (graphite) does not dissolve in the solvent, whereas ink can.