Explanation:
The attraction for a shared pair of electrons in a covalent bond depends on electronegativity. Carbon has the lowest electronegativity value of the given elements across period 2, it has the lowest effective nuclear charge (least number of protons attracting valence electrons in energy level 2). Increasing electronegativity across a period from left to right.

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

Explanation:
Saturated compounds contain only single bonds.
Butyne is an alkyne, and so, has a triple bond.

Explanation:
The sum of the oxidation state of all atoms in a compound is 0 and in an ion is equal to the charge of the ion.
O in the above molecules have an oxidation state of -2.
Group I elements have an oxidation state of +1.
In choices A, B, and C, the oxidation states of Cr on both sides are +6.
In choice D, the oxidation state of Cr changes from +6 to +3.

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

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.

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

Explanation:
Statement III is not correct as physical properties, including melting point and metallic character, change dramatically across a period due to changes in nuclear charge for the same number of shells.
Elements in the periodic table are arranged in increased atomic number.
Anions are atoms that have gained electrons. This will increase the electron-electron repulsion in the outermost shell, and will cause the electrons to move further apart. Therefore, the radius of the outershell will increase.

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

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:
In HBrO, the oxidation states of both H and Br are +1.

Explanation:

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

Explanation:
Na^+, Ne, O^2−have 10 electrons in two energy levels with 11, 10, and 8 protons respectively. The increased number of protons has a greater pull on the 10 electrons and reduces the radius.
Ca^2+ has 18 electrons in 3 energy levels and is therefore, the largest.

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:
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:

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:
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:

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

Explanation:
The oxidation state of X in choices A, B, and C is +3. The oxidation state of X in choice D is +6.

Explanation:
First ionization energy decreases down a group due to increased shielding (number of shells). Beryllium must therefore have a higher first IE than magnesium. And similarly, oxygen higher than sulfur.
First ionization energy increases across a period due to increased nuclear charge for the same number of shells. Hence, oxygen has higher first IE than beryllium.

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