physical chemistry: atomic structure
questions & Answers 100% Correct!!
Q1.Which one of the following is the electronic configuration of the strongest reducing agent?
A 1s2 2s2 2p5
B 1s2 2s2 2p6 3s2
C 1s2 2s2 2p6 3s2 3p5
D 1s2 2s2 2p6 3s2 3p6 4s2 - ANSWER D
Which one of the following ionisations requires less energy than the first ionisation energy of
oxygen?
A S(g) → S+(g) + e−
B O+(g) → O2+(g) + e−
C N(g) → N+(g) + e−
D F(g) → F+(g) + e− - ANSWER A
Which one of the following is the electronic configuration of an element with a maximum oxidation
state of +5?
A 1s2 2s2 2p5
B 1s2 2s2 2p6 3s2 3p1
C 1s2 2s2 2p6 3s2 3p3
D 1s2 2s2 2p6 3s2 3p6 3d7 4s2 - ANSWER C
Which atom has an incomplete sub-shell?
A Be
B Ca
C Ge
D Zn - ANSWER C
One isotope of sodium has a relative mass of 23.
,(i) Define, in terms of the fundamental particles present, the meaning of the term isotopes.
(ii) Explain why isotopes of the same element have the same chemical properties.
(iii) Calculate the mass, in grams, of a single atom of this isotope of sodium.(The Avogadro constant,
L, is 6.023 × 1023 mol-1) - ANSWER (a) (i) Atoms with the same number of protons / proton number
(1)
NOT same atomic number
with different numbers of neutrons (1)
NOT different mass number / fewer neutrons
(ii) Chemical properties depend on the number or amount of(outer) electrons (1) OR, isotopes have
the same electronconfiguration / same number of e-
(iii) 23/6.023 × 1023 (1)
CE = 0 if inverted or multiplied
tied to M1 3.8(2) × 10-23 [2-5 sig figs] (1)
Give the electronic configuration, showing all sub-levels, for a sodium atom. - ANSWER 1s2 2s2 2p6
3s1
Explain why chromium is placed in the d block in the Periodic Table. - ANSWER Highest energy e- /
outer e-s / last e- in (3)d sub-shell (1)
OR d sub-shell being filled / is incompleteOR highest energy sub-shell is (3)d
Which one of the following explains why boron has a lower first ionisation energy than beryllium?
A A boron atom is smaller than a beryllium atom.
B In beryllium all the electrons are paired in full sub-shells.
C A beryllium atom has fewer protons than a boron atom.
D In boron the 2p electron occupies a higher energy level than a 2s electron. - ANSWER D
Which one of the following atoms has only two unpaired electrons in its ground (lowest energy)
state?
A helium
B beryllium
C nitrogen
D oxygen - ANSWER D
,Which one of the following does not have a pair of s electrons in its highest filled electron energy
sub-level?
A H−
B Mg
C P3+
D Ar - ANSWER D
An atom has half as many protons as an atom of 28Si and also has six fewer neutrons than an atom
of 28Si. Give the symbol, including the mass number and the atomic number, of this atom. - ANSWER
15N7
Assuming that chlorine exists as two isotopes, and that hydrogen and carbon exist as one isotope
each, how many molecular ion peaks will be shown in the mass spectrum of C4H6Cl4?
A2
B3
C4
D 5 - ANSWER D
What is meant by the term first ionisation energy? - ANSWER Heat / enthalpy / energy for removal
of one electron (1)
from a gaseous atom (1)
(see diagram on page 6 of word document) what is the maximum number of electrons that can be
accommodated in an s sub-level? - ANSWER 2
What evidence from the diagram supports your answer to part - ANSWER Two elements (or Na /
Mg) before the drop (in energy) to Al (1)
What evidence from the diagram supports the fact that the 3p sub-level is higher in energy than the
3s? - ANSWER ionisation energy of Al < that for Mg (1)
What evidence from the diagram supports the fact that no more than three unpaired electrons can
be accommodated in the 3p sub-level? - ANSWER fall in energy from P to S (1)
, From Al to P there are 3 additional electrons (1)
or three elements
An atom in which the number of protons is greater than the number of neutrons is
A 234U
B 6Li
C 3He
D 2H - ANSWER C
State the meaning of the term electronegativity. - ANSWER (a) Ability (or power) of an atom to
attract electron density(or electrons or -ve charge) (1)in a covalent bond (1)
State and explain the trend in electronegativity values across Period 3 from sodium to chlorine. -
ANSWER Trend: increases (1)Explanation: nuclear charge (number of protons) increases (1)electrons
in same shell (1)
OR similar shieldingOR atoms similar size or smallerOR 1 mol of e-
State the relative charge and relative mass of a proton, of a neutron and of an electron.In terms of
particles, explain the relationship between two isotopes of the same element.Explain why these
isotopes have identical chemical properties. - ANSWER (a) Proton: mass 1, charge + 1 (1)Neutron:
mass 1, charge 0 (1)Electron mass 1/1840, charge -1 (1)
Allow mass = 0, or negligible, or 1/1800 to 1/2000
Isotopes have the same number of protons (1)
OR atomic number
different number of neutrons (1)
Isotopes have the same electronic configuration (1)
OR same number of electrons
Chemical properties depend on electrons (1)
Define the term relative atomic mass. An element exists as a mixture of three isotopes.Explain, in
detail, how the relative atomic mass of this element can be calculated from data obtained from the
mass spectrum of the element. - ANSWER Average mass of atom/isotope/mass of 1 carbon 12 atom
(1)
questions & Answers 100% Correct!!
Q1.Which one of the following is the electronic configuration of the strongest reducing agent?
A 1s2 2s2 2p5
B 1s2 2s2 2p6 3s2
C 1s2 2s2 2p6 3s2 3p5
D 1s2 2s2 2p6 3s2 3p6 4s2 - ANSWER D
Which one of the following ionisations requires less energy than the first ionisation energy of
oxygen?
A S(g) → S+(g) + e−
B O+(g) → O2+(g) + e−
C N(g) → N+(g) + e−
D F(g) → F+(g) + e− - ANSWER A
Which one of the following is the electronic configuration of an element with a maximum oxidation
state of +5?
A 1s2 2s2 2p5
B 1s2 2s2 2p6 3s2 3p1
C 1s2 2s2 2p6 3s2 3p3
D 1s2 2s2 2p6 3s2 3p6 3d7 4s2 - ANSWER C
Which atom has an incomplete sub-shell?
A Be
B Ca
C Ge
D Zn - ANSWER C
One isotope of sodium has a relative mass of 23.
,(i) Define, in terms of the fundamental particles present, the meaning of the term isotopes.
(ii) Explain why isotopes of the same element have the same chemical properties.
(iii) Calculate the mass, in grams, of a single atom of this isotope of sodium.(The Avogadro constant,
L, is 6.023 × 1023 mol-1) - ANSWER (a) (i) Atoms with the same number of protons / proton number
(1)
NOT same atomic number
with different numbers of neutrons (1)
NOT different mass number / fewer neutrons
(ii) Chemical properties depend on the number or amount of(outer) electrons (1) OR, isotopes have
the same electronconfiguration / same number of e-
(iii) 23/6.023 × 1023 (1)
CE = 0 if inverted or multiplied
tied to M1 3.8(2) × 10-23 [2-5 sig figs] (1)
Give the electronic configuration, showing all sub-levels, for a sodium atom. - ANSWER 1s2 2s2 2p6
3s1
Explain why chromium is placed in the d block in the Periodic Table. - ANSWER Highest energy e- /
outer e-s / last e- in (3)d sub-shell (1)
OR d sub-shell being filled / is incompleteOR highest energy sub-shell is (3)d
Which one of the following explains why boron has a lower first ionisation energy than beryllium?
A A boron atom is smaller than a beryllium atom.
B In beryllium all the electrons are paired in full sub-shells.
C A beryllium atom has fewer protons than a boron atom.
D In boron the 2p electron occupies a higher energy level than a 2s electron. - ANSWER D
Which one of the following atoms has only two unpaired electrons in its ground (lowest energy)
state?
A helium
B beryllium
C nitrogen
D oxygen - ANSWER D
,Which one of the following does not have a pair of s electrons in its highest filled electron energy
sub-level?
A H−
B Mg
C P3+
D Ar - ANSWER D
An atom has half as many protons as an atom of 28Si and also has six fewer neutrons than an atom
of 28Si. Give the symbol, including the mass number and the atomic number, of this atom. - ANSWER
15N7
Assuming that chlorine exists as two isotopes, and that hydrogen and carbon exist as one isotope
each, how many molecular ion peaks will be shown in the mass spectrum of C4H6Cl4?
A2
B3
C4
D 5 - ANSWER D
What is meant by the term first ionisation energy? - ANSWER Heat / enthalpy / energy for removal
of one electron (1)
from a gaseous atom (1)
(see diagram on page 6 of word document) what is the maximum number of electrons that can be
accommodated in an s sub-level? - ANSWER 2
What evidence from the diagram supports your answer to part - ANSWER Two elements (or Na /
Mg) before the drop (in energy) to Al (1)
What evidence from the diagram supports the fact that the 3p sub-level is higher in energy than the
3s? - ANSWER ionisation energy of Al < that for Mg (1)
What evidence from the diagram supports the fact that no more than three unpaired electrons can
be accommodated in the 3p sub-level? - ANSWER fall in energy from P to S (1)
, From Al to P there are 3 additional electrons (1)
or three elements
An atom in which the number of protons is greater than the number of neutrons is
A 234U
B 6Li
C 3He
D 2H - ANSWER C
State the meaning of the term electronegativity. - ANSWER (a) Ability (or power) of an atom to
attract electron density(or electrons or -ve charge) (1)in a covalent bond (1)
State and explain the trend in electronegativity values across Period 3 from sodium to chlorine. -
ANSWER Trend: increases (1)Explanation: nuclear charge (number of protons) increases (1)electrons
in same shell (1)
OR similar shieldingOR atoms similar size or smallerOR 1 mol of e-
State the relative charge and relative mass of a proton, of a neutron and of an electron.In terms of
particles, explain the relationship between two isotopes of the same element.Explain why these
isotopes have identical chemical properties. - ANSWER (a) Proton: mass 1, charge + 1 (1)Neutron:
mass 1, charge 0 (1)Electron mass 1/1840, charge -1 (1)
Allow mass = 0, or negligible, or 1/1800 to 1/2000
Isotopes have the same number of protons (1)
OR atomic number
different number of neutrons (1)
Isotopes have the same electronic configuration (1)
OR same number of electrons
Chemical properties depend on electrons (1)
Define the term relative atomic mass. An element exists as a mixture of three isotopes.Explain, in
detail, how the relative atomic mass of this element can be calculated from data obtained from the
mass spectrum of the element. - ANSWER Average mass of atom/isotope/mass of 1 carbon 12 atom
(1)
