Download Atomic radius decreases across a period due to the increasing

1. Atomic radius decreases across a period due to the increasing effective
nuclear charge. Atomic number, electronegativity and first ionization energy
all increase across a period.
Correct answer is C.
2. The only incorrect statement is III as oxides of elements on the left of a period
are ionic and therefore basic. Oxides of elements on the right of a period are
covalent and therefore acidic.
Correct answer is A.
3. Electronegativity decreases down Group 17 due to the valence electrons
being in shells that are further removed from the nucleus. Melting point,
atomic radius and ionic radius all increase down Group 17.
Correct answer is B.
4. Covalent oxides are acidic oxides’. P4O10and SO3are covalent oxides so will
produce acidic solutions when added to water. (MgO is an ionic oxide and will
produce a basic solution.)
Correct answer is B.
5. Electronegativity increases across Period 3. The ionic radius and the atomic
radius decrease across Period 3. Melting point increases for the metallic and
metalloid elements Li, Be and B until a maximum is reached for carbon (which
is a network solid), then decreases for N, O and F, which exist as diatomic
molecules, and Ne, a noble gas, all with weak intermolecular forces.
Correct answer is A.
6. The best definition for electronegativity is the attraction of an atom for a
bonding pair of electrons.
Correct answer is B.
7. The equation for the exothermic reaction of sodium with water is 2Na(s) +
2H2O(l) →2NaOH(aq) + H2(g). NaOH(aq) is a colourless solution, bubbles will
be observed due to formation of H2(g) and the temperature will increase due
to it being an exothermic reaction.
Correct answer is D.
8. The equation for the reaction of chlorine with water is Cl2(g) + H2O(l) →
HOCl(aq) + HCl(aq).
Correct answer is C.
9. There are four Cl–ligands attached to the copper ion. The copper ion must be
Cu2+(and have an oxidation number of +2) to give an overall 2− charge. As
there are four Cl−ligands attached to the Cu2+ion the coordination number is 4.
All three statements are correct.
Correct answer is D.
10. Complex I: H2O is a neutral ligand. The iron oxidation number must be +3 to
give an overall charge of +3.Complex II: H2O is a neutral ligand and CN−is
negatively charged. The iron oxidation number must be +3 to give an overall
charge of +2.Complex III: CN− is a negatively charged ligand. The iron
oxidation number must be +3 to give an overall charge of –3.
Correct answer is D.
11. V2O5 is the catalyst used in the Contact process for the conversion of SO2(g)
to SO3(g).
Correct answer is C.
12. Transition metal complexes are coloured due to the absorption of visible light,
which results in the excitation of an electron from a low energy d orbital to a
higher energy d orbital.
Correct answer is C.
13. (a)The first ionization energy is the energy required to remove one mole of
electrons from one mole of atoms in the gaseous state.
(b) Magnesium has more protons and therefore a greater effective nuclear
charge than sodium so its valence electrons experience a greater electrostatic
attraction to the nucleus. More energy is therefore required to ionize
magnesium and remove a valence electron.
14. Sodium oxide:Na2O(s) + H2O(l) →2NaOH(aq)
Na2O is a basic oxide as
basic NaOH formed.Sulfur trioxide:SO3(l) + H2O(l) →H2SO4(aq)SO3 is an
acidic oxide as acidic H2SO4 formed.
15. (a)Because chlorine is more electronegative than iodine the iodide ions are
displaced by chlorine and the solution will turn orange/brown due to the
formation of aqueous iodine, I2(aq).Cl2(aq) + 2KI(aq) →2KCl(aq) + I2(aq)(An
alternative equation that omits the K+ spectator ions is:
Cl2(aq) + 2I–(aq) →2Cl–(aq) + I2(aq))
(b) Because fluorine is more electronegative than chlorine it is more reactive
and the fluoride ions cannot be displaced by chlorine so no reaction occurs.
No colour change will be observed.
16. (a)Elements are arranged according to increasing atomic number (Z).
(b) Electronegativity increases across Period 3 as the effective nuclear charge
increases. The larger number of protons in the nucleus exerts a greater
electrostatic attraction on a bonded pair of electrons. As the electrons are
being added in the same valence shell they do not screen other valence
electrons such as a bonded pair and reduce their attraction to the nucleus.
The best definition of electronegativity is the attraction of an atom to a bonded
pair of electrons. As noble gases do not readily form covalent bonds they are
not capable of attracting a bonded pair of electrons and are therefore not
assigned electronegativity values.
17 . (a) (i) The sodium ion has a greater effective nuclear charge than the sodium
atom as they both have 11 protons but the ion has 10 electrons compared to
the atom, which has 11. The greater effective nuclear charge on the sodium
ion attracts the electrons closer to the nucleus than in the atom.
(ii) The electron configuration of Na is 1s22s22p63s1.The electron configuration
of Na+ is 1s22s22p6.Because the valence electrons of the sodium ion are in the
second level it will have a smaller radius than the sodium atom, where the
valence electron is in the third energy level and further from the nucleus.
(b) P3– has electron configuration 1s22s22p63s22p6. Si4+ has electron
configuration 1s22s22p6.Because the valence electrons of P3–are in the third
energy level and the valence electrons of Si4+are in the second energy level,
P3– will have the greater ionic radius.
18. (a)Although it contains charged ions, Na2O is unable to conduct electricity in the
solid state as the ions are not able to move.
(b) 2O2–(l) →O2(g) + 4e–(or O2–(l) →½O2(g) + 2e–)
(c) (i) Sodium oxide is a basic oxide. (Sodium oxide is ionic and ionic oxides are
basic oxides.)
(ii) Na2O(s) + H2O(l) →2NaOH(aq) (or Na2O(s) + H2O(l) →2Na+(aq) + 2OH–(aq))
19 (a)The first ionization energy is the energy required to remove one mole of
electrons from one mole of atoms in the gaseous state: M(g) →M+(g) + e–.
Periodicity is the repeating pattern of physical and chemical properties of elements.
(b) The electron configuration of argon is 1s22s22p6.As the valence electrons of
elements in the same period are in the same shell they do not effectively screen
each other so the electrons of the noble gases experience the greatest effective
nuclear charge as these elements have the most protons of the elements in
their period. The valence electrons of the noble gases therefore experience the
greatest attraction to the nucleus, which is why they have the highest ionization
energies of the elements in each period.
(c) The valence electrons of sodium and chlorine are both in the third shell so they
experience similar shielding effects. However, chlorine has 17 protons and sodium
has 11 protons so the valence electrons of chlorine will experience a greater
attraction to the nucleus and be held closer to the nucleus, resulting in a smaller
atomic radius.
(d)Sulfide, S2–, and chloride, Cl, are isoelectronic, both having 18 electrons.
However, sulfide has 16 protons and chloride has 17 protons. This means the
sulfide valence electrons experience less attraction to the nucleus and will be held
less closely, resulting in a larger ionic radius.
(e)The Group 1 elements are metals and metallic bond strength (see Chapter 4)
decreases down the group as the delocalized valence electrons are in energy levels
that are more distant from the nucleus of the cations and experience a weaker
electrostatic attraction to the nuclei. The weaker metallic bond strength results in
lower melting points going down the group. The Group 17 elements exist as
diatomic molecules, X2, which are attracted to each other by weak London
dispersion forces
London dispersion forces increase down the group as the atoms
become larger and contain more electrons, resulting in higher melting points.
20 (a)The square brackets indicate that [Cu(H2O)6]2+is a complex ion where the
charge is delocalized over the whole complex whose chemical formula is written
within the brackets.
(b) The d electrons in [Cu(H2O)6]2+are split into two energy levels. The transition of
an electron from a low energy d orbital into a higher energy d orbital results in the
absorption of visible light and the complex therefore appears coloured. The colour
observed is complimentary to the colour of the light absorption