Explanation​:
Amides have a C=O and C−N on the same central carbon atom.

Explanation:

The group of an element is determined by its atomic number, which is found in the lower left corner of the element symbol. Although this conflicts with the representation in the data booklet, students should be able to differentiate between the mass and atomic number based on their relative size. The elements represented by options A, B, C and D are calcium (an alkaline earth metal), iron (a transition metal), gallium (a poor / p block metal) and rubidium (an alkali metal), respectively. This question is moderately difficult as the student must identify the correct value from the given symbol and relate it to the position of an element in the periodic table.

Explanation​:
Increasing atomic radius results in a weaker electrostatic force of attraction between the nucleus and electrons in the covalent bond. An increased number of shells down the group increases the shielding between the nucleus and electrons in the covalent bond.

Explanation:​

Metalloids lie on the boundary between metals and non-metals in the p block of the periodic table. They are shiny like metals but brittle like non-metals, and can switch between being electrical insulators and electrical conductors. Although this switchable conductivity could be considered as a change from metal-like to non-metal-like behaviour, it does not affect all properties of the element: the element does not switch from being a metal to a non-metal.

Metalloids do not contain incomplete d subshells (this is a property of transition metals) and lie alongside the poor metals in the p block of the periodic table. This question is categorised as moderately difficult as the concept of metalloids is not covered extensively in the syllabus, though the distinction between metals, non-metals and metalloids is highlighted.

Explanation​:
NH2​ is the amine functional group, RCOOR′ is the ester functional group.

Explanation​:
Strontium is in group 2 and so forms Sr^2+ ions. The formula of the sulfide ion is S^2− as sulfur is in group 16. For the positive and negative charges to cancel out, one of each ion is required.

Explanation​:
A tertiary amine is when three carbon groups are attached to the amine.

Explanation​:
The two compounds are part of a homologous series because they have the same functional group but different hydrocarbon chains. Both compounds are alcohols, so interact via hydrogen bonding.
The CH2​ and CH3 groups of the alkyl chains, however, interact via weaker dispersion forces, as they contain only non-polar bonds. Increasing the length of the alkyl chain does not affect the strength of hydrogen bonding, but the strength of the dispersion forces is increased. More heat energy is needed to separate molecules of Y, so the boiling point is higher.

Explanation:​

Lithium is in group 1 and so forms Li+ ions. The formula of the nitride ion is N^3−as nitrogen is in group 15. For the positive and negative charges to cancel out, three Li+ ions are needed for each N^3− ion.

Explanation​:
The number of shells and therefore the shielding effect is the same for all of these species.
As the number of protons decreases, the attraction between the nucleus and electrons decreases, resulting in a smaller radius.
K^+ has the most protons (19), whereas S^2− has the least (16).

Explanation:​
First ionization energy is defined as the energy required to remove one mole of electrons from one mole gaseous atoms.

Explanation:​

The atomic number of Cr is higher than that of V by 1, and its relative atomic mass is also higher by approximately 1. The atomic number is unique for each element and dictates the position of the element in the periodic table; thus, Cr always has an atomic number of 24 and vanadium an atomic number of 23. However, isotopes of an element may have different atomic masses, so an atom of Cr may have a lower atomic mass than an atom of V. This question is categorised as easy since the difference between atomic number and atomic mass and the variation in mass between isotopes of an element are covered extensively in the syllabus.

Explanation:​
Acid rain is formed from sulfur and nitrogen oxides dissolving in the clouds.

Explanation:​
The 6 protons in the nucleus of carbon will exert a stronger attractive force on the second energy level electrons than the 5 protons of boron.
Increasing electron affinity from left to right across a period.

Explanation:​
The air is naturally composed of 0.04% carbon dioxide, which dissolves in water to form the weak carbonic acid

Explanation:​

The names of the labelled groups are covered explicitly in the syllabus.

Explanation:​
C3H6​ belongs to the alkene class with the general formula CnH2n​, and has a three carbon chain.

Explanation:
Ethers contain C−O single bonds $\text{not}$ the $\mathrm{C}=\mathrm{O}$ carbonyl group.

Explanation​:
Structural isomers have the same molecular formula but different structural formulae.
Methoxyethane and propanol both have the molecular formula C3H8O.

Explanation​:
Recall that the functional group is carboxyl and the class or series is carboxylic acid.

Explanation​:
The molecular formula of pentan-2-one is C5H10O

There are 5 C atoms and 10 H atoms, so the combustion produces 5115​ = 5 moles of CO2​ and 102210​ = 5 moles of H2O per mole of pentan-2-one. The value of b is therefore 5.0.

There are $15$ O atoms on the right-hand side of the equation but only 1 O atom in petan-2-one, so the compound must react with (15−1)/2​ = 7 moles of O2​. The value of a is therefore 7.0.

Explanation:​
Choices III and IV are ethene and ethyne with a double bond and a triple bond, respectively. They belong to the classes of alkenes and alkynes, which can be deduced by the general formulae, CnH2n​ and CnH2n−2 .
Choice I is the alkane methane, and choice II is a halogenoalkane (chloromethane).

Explanation:​
Atomic radius and metallic character decrease across a period. Ionization energy decreases down a group due to increased shielding.

Explanation:​
Group 17 melting points increase down the group due to increased strength in intermolecular forces. The molecular structures of each element are held together by London (dispersion) forces. These increase with the number of electrons in the molecule. Therefore statement I is not true, but III is.
Group 1 melting points decrease down a group due to decreasing metallic bond strength (with increase of atomic radius), therefore statement II is also true.