3.1.1 Atomic structure

Question 1

Isotopes

Answer 1

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

Question 2

What can mass spectrometry be used for?

Answer 2

1. find the abundance and mass of each isotope in an element

2. find the relative molecular mass of substances made of molecules

Question 3

Two types of ionisation

Answer 3

Electron impact and electrospray ionisation

Question 4

Electron impact

Answer 4

High energy electrons are fired from a hot cathode at the sample. This knocks off one electron and forms a positive ions

Question 5

Equation for electron impact

Answer 5

X(g) ￫ X+(g) + e-

Question 6

Electrospray ionisation

Answer 6

Sample dissolved in volatile solution and injected through a fine hypodermic needle giving a fine mist. The tip of the needle has a high voltage and each atom gains a proton as it leaves the needle.
Forming a positive ion

Question 7

When is electrospray ionisation used?

Answer 7

On molecules with a high Mr value as using electron impact can cause fragmentation

Question 8

What type of molecules travel faster in acceleration?

Answer 8

lighter particles travel faster

Question 9

How many electrons can electron orbital hold?

Answer 9

2

Question 10

What are orbitals

Answer 10

Regions of space that electrons are most likely to be in

Question 11

Aufbau principle

Answer 11

Electrons enter the lowest orbital available

Question 12

Hunds rule

Answer 12

Electrons prefer to enter orbitals on their own, they only pair up when no empty orbitals of the same energy are available.

Question 13

4s and 3d orbital?

Answer 13

The 4s orbital fills up before the 3d orbital. However, when losing electrons, electrons are lost from the 4s before the 3d.

Question 14

First ionisation energy

Answer 14

The energy required to remove one mole of electrons from one mole of gaseous atoms to provide one mole of gaseuous single charged ions.

Question 15

Ionisation energy is affected by…

Answer 15

• Atomic radius
• number of protons
• shielding

Question 16

Along a period the first ionisation energy…

Answer 16

increases because the atomic radius decreases due to more protons and the same amount of shielding

Question 17

Down a group the fist ionsation energy…

Answer 17

decreases because the atomic radius increases and shielding increases.

Question 18

Successive ionisation

Answer 18

A big jump indicates a change in energy level.

Question 19

How do you find the relative atomic mass?

Answer 19

m/z x abundance / total abundance