Year 9 Summer Revision: Atoms, Elements, and Compounds

Comprehensive practice questions covering atomic structure, periodic table trends, chemical reactions, separation techniques, and water treatment based on the Year 9 summer revision notes.

What is an element?

A substance that is made of only one sort of atom.

How are metals and non-metals arranged in the periodic table?

Metals appear on the left hand side, and non-metals appear on the right hand side.

What are the charges and relative masses of protons, neutrons, and electrons?

Proton: Charge $+1$, Mass $1$; Neutron: Charge $0$, Mass $1$; Electron: Charge $-1$, Mass $0$.

Why are atoms neutral?

Because the number of electrons equals the number of protons in the nucleus.

What defines which element an atom is?

The number of protons determines the element (e.g., $12$ protons is carbon).

What are isotopes?

Atoms of the same element with different numbers of neutrons.

What is the maximum number of electrons in the first three energy shells?

The 1st energy shell holds up to $2$ electrons, while the 2nd and 3rd shells hold a maximum of $8$ electrons each.

How is the group number of an element related to its electron arrangement?

The group number equals the number of outer shell electrons.

What is the chemical formula for aluminium nitrate?

$$Al(NO_3)_3$$

What is the formula for methane and sulfuric acid?

Methane is $CH_4$ and sulfuric acid is $H_2SO_4$.

What is the Law of Conservation of Mass in a chemical reaction?

No atoms are lost or made during a reaction, so the mass of the products equals the mass of the reactants.

How is distillation used as a separation technique?

It is used to separate a liquid from a mixture by evaporation followed by condensation.

What is the formula for calculating an $Rf$ value in chromatography?

$$Rf = \frac{\text{distance moved by the substance}}{\text{distance moved by the solvent}}$$

What was the Plum-pudding model of the atom?

A model suggesting that the atom was a ball of positive charge with negative electrons embedded in it.

How did Mendeleev overcome problems with early periodic tables?

He left gaps for elements that he thought had not been discovered yet.

Why are Group 0 (Noble Gases) chemically unreactive?

They are monatomic gases with a full outer shell of electrons, which is a stable arrangement.

What is the general word equation for Group 1 metals reacting with water?

$$\text{METAL} + \text{WATER} \rightarrow \text{METAL\,HYDROXIDE} + \text{HYDROGEN}$$

What is the reactivity trend in Group 1 (Alkali Metals)?

Reactivity increases down the group because the outer electron is further and more shielded from the nucleus, making it easier to lose.

List four properties of Transition Metals compared to Group 1 metals.

They have higher melting/boiling points, higher densities, are stronger/harder, and are much less reactive.

What happens to the melting and boiling points of Group 7 (Halogens) as you go down the group?

As molecules get larger, the strength of the weak intermolecular forces increases, so the melting and boiling points increase.

What is a displacement reaction between halogens?

A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt.

Define potable water.

Water that is safe to drink and has sufficiently low levels of dissolved salts and microbes.

What are the common sterilising agents for treating fresh water?

Chlorine, ozone, or ultra-violet light.

What is the percentage composition of Nitrogen and Oxygen in the air?

Nitrogen = $78\%$ and Oxygen = $21\%$.

Is the reaction $Cu^{2+}(aq) + Fe(s) \rightarrow Fe^{2+}(aq) + Cu(s)$ an example of oxidation or reduction for iron?

$Fe$ loses electrons, which is oxidation.

What ion makes a solution acidic?

Hydrogen ions, $H^+(aq)$.

What ion makes a solution alkaline?

Hydroxide ions, $OH^-(aq)$.

What is the difference between a strong acid and a weak acid?

A strong acid is completely ionised in water (e.g., $HCl$), while a weak acid is only partially ionised (e.g., ethanoic acid).

What is the general ionic equation for neutralisation?

$$H^+(aq) + OH^-(aq) \rightarrow H_2O(l)$$

What salt is produced by reacting sulfuric acid with magnesium?

Magnesium sulfate ($MgSO_4$).

In a titration, what is the colour of Phenolphthalein in acid and alkali?

Colourless in acid and pink in alkali.

What are concordant results in a titration?

Two results that are within $0.1\,cm^3$ of each other.