Atomic structure and emission spectra

Question 1

Isotope def

Answer 1

Different versions of an element with the same number of protons but different number of neutrons

Question 2

Relative isotopic mass

Answer 2

Mass of a particular isotope of an element relative to one twelfth of mass of carbon-12.

Question 3

Relative atomic mass

Answer 3

Weighted average of all naturally occurring isotopes of an element relative to one twelfth of mass of carbon 12.

Question 4

First ionisation energy def

Answer 4

Energy required to remove one mole of electrons from one mole of gaseous atoms.
M(g) -> M+(g) + e-

Question 5

2nd ionisation energy etc.

Answer 5

Energy required to remove one mole of electrons from one mole of 1+ (and etc.) gaseous ions.

Question 6

Things that govern ionisation energy

Answer 6

Nuclear charge

Electron shielding, electron shielding is a much more significant factor than nuclear charge.

Question 7

Why does first ionisation energy decrease down group 1?

Answer 7

Despite nuclear charge up, number of shells up, meaning more shielding between nucleus and outer electron and less effective nuclear charge so less energy required to remove it.

Question 8

Why general increase in first ionisation energy across a period?

Answer 8

Nuclear charge increases with number of protons. Same shells therefore similar shielding.

Question 9

How is atomic emission spectra made?

Answer 9

Made by exciting electrons via heat/electricity to excite them to higher energy level. As they go back down to lower energy levels, specific wavelengths of electromagnetic radiation is emitted and detected.

Question 10

What does a line spectra prove?

Answer 10

That electrons can only exist at certain energy levels (shells) rather than any as only certain energy transitions are possible.

Question 11

What is successive ionisation?

Answer 11

Sequential removal of all electrons surrounding an atom from highest energy level to lowest. Each electron removed requires more energy.

Question 12

Why is successive ionisation energy much higher when going to a new shell?

Answer 12

Reduced shielding, Z eff increased, more attraction.

Also proof for shells.

Question 13

How many orbitals in an s, p and d subshell?

Answer 13

1, 3, 5

Question 14

Shape of each subshell

Answer 14

Google it

Question 15

What is up spin?

Answer 15

+1/2 or half arrow upwards

Question 16

What is down spin?

Answer 16

-1/2 or half arrow downwards

Question 17

What is orbital?

Answer 17

Region within an atom that can hold up to two electrons with opposite spins. 90% chance of finding electron inside.

Question 18

What is Hund’s rule of Maximum Multiplicity?

Answer 18

Electrons in the same subshell will fill all available orbitals singly before pairing in the same orbital as it minimises electron repulsion.

Question 19

Pauli’s Exclusion principle

Answer 19

No two electrons can have the same 4 quantum numbers and so if the electrons are in the same orbital, they must have opposite spin.

Question 20

Order that subshells fill

Answer 20

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, order on periodic table

Question 21

Aufbau principle

Answer 21

Electrons must fill orbitals from lowest energy state - ‘ground state’.

Question 22

Electron config of Cr

Answer 22

[Ar] 4s1 3d5

Question 23

Electron config of Cu

Answer 23

[Ar] 4s1 3d10

Question 24

Why is the electron config of Cr and Cu different?

Answer 24

To reduce repulsion in the 4s shell, a 4s electron is promoted to the 3d subshell to create a half/fully filled shell which is at a lower energy state.

Question 25

Ionisation of transition metals

Answer 25

Remove 4s electrons first when ionising

Question 26

What part of an element determines its chemical properties

Answer 26

Electronic config

Question 27

Why does first ionisation energy decrease from Be to B despite nuclear charge increasing?

Answer 27

This is because the outer electron removed in B is from the 2p subshell and therefore has increased shielding from the 2s subshell electrons. Zeff is therefore lower and less energy is required to remove electron.

Question 28

Why does first ionisation energy decrease from N to O despite nuclear charge increasing?

Answer 28

The outer electron in O is paired in the 2p subshell whereas in N it is not. Therefore, there is increased electron repulsion and less energy is required to remove the electron.