Atomic Structure

Question 1

Identify and describe protons, neutrons and electrons in terms of their relative charges and relative masses

Answer 1

Mass, charge
Proton- 1, +1
Neutron- 1, 0
Electron- 1/1840 (negligible), -1

Question 2

Deduce the behaviour of beams of protons, neutrons and electrons in an electric field

Answer 2

Angle of deflection is proportional to charge/mass

Question 3

Define isotopes

Answer 3

Atoms of the same element with same number of protons but different number of neutrons

Question 4

Write the electronic configuration for 14Si

Answer 4

1s2 2s2 2p6 3s2 3p2

Question 5

Write the electronic configuration for 35Br+

Answer 5

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4

Question 6

Write the electronic configuration for 16S2-

Answer 6

1s2 2s2 2p6 3s2 3p6

Question 7

Write the electronic configuration for 29Cu

Answer 7

1s2 2s2 2p6 3s2 3p6 3d10 4s1

Question 8

Write the electronic configuration for 24Cr

Answer 8

1s2 2s2 2p6 3s2 3p6 3d5 4s1

Question 9

Draw the shape of d(xy) orbital

Answer 9

Two lobed orbitals, both cutting origin along xy plane

Question 10

Draw the shape of d(x^2-y^2)

Answer 10

Two lobed orbitals, one lying on x-axis other lying on y axis

Question 11

Draw the shape of d(z^2)

Answer 11

One lobed orbital on z axis with a donut orbital round the middle

Question 12

First ionisation energy ____ down the Group, because ____

Answer 12

First ionisation energies GENERALLY decrease down the Group
The number of electron shells increases, increasing shielding experienced by the valence electrons and the distance between the nucleus and valence electrons.

Despite increasing nuclear charge, electrostatic forces of attraction between the nucleus and valence electrons decreases hence it requires less energy to remove a valence electron down the Group.

Question 13

First ionisation energy ____ across the Period, because ____

Answer 13

First ionisation energies GENERALLY increase across the Period
The number of electron shells remains the same while the number of protons increases, hence shielding experienced by valence electrons is the same. Due to increasing effective nuclear charge, electrostatic attraction between nucleus and valence electrons increases and more energy is required to remove a valence electron across the Period.

Question 14

Why is the first ionisation energy of B lower than Be?

Answer 14

B: 1s2 2s2 2p1
Be: 1s2 2s2

The 2p removed from B is from a higher energy subshell than the 2s electron removed from Be. Hence it required less energy to remove the electron from B.

Question 15

Which first ionisation energy is higher: N or O?

Why?

Answer 15

N: 1s2 2s2 2p3 (11)(11) (1)(1)(1)
O: 1s2 2s2 2p4 (11)(11) (11)(1)(1)

The electron removed from O was a paired electron while the electron removed from N was an unpaired electron. Hence the electron removed from O experienced inter-electronic repulsion and required less energy to remove.

Question 16

Explain the large jump between the 5th and 6th ionisation energies of this element, and deduce which Group the element is from.

Answer 16

Group 15.
Since significantly more energy is required to remove the 6th electron, this means that the 6th electron came from an inner quantum shell nearer to nucleus which experiences stronger electrostatic attraction to the nucleus. Hence the atom has 5 valence electrons and is from Group 15.

Question 17

Explain the small jumps in successive ionisation energies of an atom of an element.

Answer 17

Small jumps are caused when an electron is moved from a lower energy subshell, which requires more energy to remove

Question 18

Define electronegativity

Answer 18

The ability of an atom in a molecule to attract bonding electrons towards itself

Question 19

When electrostatic attraction between the nucleus and the valence electrons decreases, what happens to the following?

1) atomic radius
2) ionic radius
3) ionisation energy
4) electronegativity

Answer 19

1) atomic radius increases
2) ionic radius increases
3) ionisation energy decreases
4) electronegativity decreases

Question 20

Aufbau Principle: Electrons fill orbitals from…

Answer 20

Electrons fill orbitals from the lowest energy orbital upwards.

Question 21

Pauli Exclusion Principle: Each orbital can hold… and they must be…

Answer 21

Each orbital can hold a maximum of two electrons and they must be of opposite spins.

Question 22

Hund’s Rule: Degenerate orbitals of a subshell must be occupied …

Answer 22

Degenerate orbitals of a subshell must be occupied singly by electrons of parallel spins before pairing can occur, to minimise inter-electronic repulsion.

Question 23

An atom is in the ground state when…

Answer 23

An atom is in the ground state when the electrons are the in the orbitals of lowest available energy level.

Question 24

An atom is in the excited state when…

Answer 24

An atom is in the excited state when electrons absorb energy and are promoted to a higher energy level. They are unstable and can emit energy to return to the ground state.

Question 25

Successive ionisation energies of a same element ____ because ____

Answer 25

Successive ionisation energies of a same element increase, because each successive electron is removed from an increasingly positively-charged ion which attracts the electrons more strongly.