(I) Topic 1 - Atomic Structure

Question 1

What is the plum pudding model?

(History of the atom)

Answer 1

Discovered using cathode rays, it says atoms are mad up of a positively charged cloud with tiny negative embeded charge, called electrons.

Question 2

What was the last subatomic particle to be discovered and why?

(History of the atom)

Answer 2

The nucleus, as it has no charge.

Question 3

What are two differences between the plum pudding model and the modern atom?

(History of the atom)

Answer 3

1. In the modern model, electrons are in energy levels, whilst in the plum pudding model they are embedded.
2. In the modern model, the nucleus is small and dense compared to being a cloud in the plum pudding model.

Question 4

What are the 4 stages of Mass Spectrometry

Answer 4

1. Ionisation - through electrospray or electron bombardment/ impact
2. Acceleration
3. Drift Flight Tube
4. Detection

Question 5

How does Electron Bombardment/ Impact work?

(Mass Spectrometry)

Answer 5

A high energy electron gets fired from an electron gun at a sample, which knocks off an outer electron, creating a positively charged ion.

Question 6

How does Electrospray work? Write an equation.

(Mass Spectrometry)

Answer 6

The sample is dissolved in a volatile substance and passes through a thin, positively charged needle. As it does so, it picks up a proton, becoming positively charged.

(This also increases the mass of the sample)

M + H^+ —> MH^+

Question 7

What is Acceleration?

(Mass Spectrometry)

Answer 7

All ions are accelerated using an electric field so they all have the same kinetic energy

Question 8

How does the flight tube work?

(Mass Spectrometry)

Answer 8

Ions set off along the flight tube at the same time, but lighter ions start to travel faster, meaning they reach the detector first.

Question 9

How does detection occur?

(Mass Spectrometry)

Answer 9

Positvely charged ions hit a negatively charged plate, and the ions gain electrons. This generates movement of electrons, forming an electric current that can be measured.

Question 10

What occurs after detection?

(Mass Spectrometry)

Answer 10

A computer processes the data and creates a mass spectrum to show the abundance and m/z (mass:charge ratio) of every ion reaching detection.

(If the charge of an ion is a 1+, the m/z is just the mass)

Question 11

What are fragments

(Mass Spectrometry)

Answer 11

During electron bombardment/ impact, instead of knocking an outer elctron off, the electron fired breaks a bond instead, creating two smaller molecules.

Question 12

What is the A-Level structure of electrons

(Electron Configuration)

Answer 12

• Electrons are in energy levels, e.g. 1, 2, 3 etc.
• Inside energe levels are sub energy levels, e.g. s, p, d
• Inside subs shells are orbitals, where electrons are found.

Question 13

How many electrons can each orbital hold?

(Electron Configuration)

Answer 13

2

Question 14

What is the Electron configuration of Krypton?

(Electron Configuration)

Answer 14

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6

or [Ar]4s2, 3d10, 4p6

Question 15

How do electrons prefer to occupy orbitals?

(Electron Configuration)

Answer 15

Electrons prefer to occupy orbitals on their own, and only pair up when no empty orbital are available.

Question 16

What are the rules when loosing electrons from orbitals?

(Electron Configuration)

Answer 16

Electrons are lost from highest energy levels first.
Exception: electrons are lost from 4s before 3d, however are gained as normal.

Question 17

What is the exception of the expected pattern of electrons shells and orbitals? and why?

(Electron Configuration)

Answer 17

Cr and Cu, as it is energetically favourable to half fill or completely fill a d orbital.
Cr - [Ar] 4s1, 3d5
Cu - [Ar] 4s1, 3d10

Question 18

What three factors effect Ionisation Energy?

(Ionisation Energies)

Answer 18

1. Atomic Radius (distance from nucleus)
2. Nuclear charge
3. Shielding

Question 19

How does atomic radius effect ionisation energies?

(Ionisation Energies)

Answer 19

Greater Distance = weaker elecreostatic attraction so less energy required to remove the outer electron

Question 20

How does Nuclear Charge effect Ionisation Energies?

(Ionisation Energies)

Answer 20

Greater Nuclear charge = more protons = stronger electrostatic attraction, so takes more energy to remove the electron.

Question 21

How does shielding affect Ionisation Energy?

(Ionisation Energies)

Answer 21

Inner shells of electrons shield outer electrons from the neuclear charge. The more shielding the weaker the elctrostatic attraction.

Question 22

Why is there a general trend of decrease of 1st ionisation energies going down a group.

(Ionisation Energies)

Answer 22

As you go down a group, the atoms have greater nuclear charge, but also increased shielding resulting in no overall effect. However, there is a greater atomic radius as you go down the group, resulting in weaker electrostatic attraction and less energy required to remove the outer electron, decreasing the 1st ionisation energy.

Question 23

Why is there a general trend for increase in ionisation energy across a period?

(Ionisation Energies)

Answer 23

As you go across a period, There is a greater atomic charge, which also results in a decrease in atomic radius, whilst there is no increased shielding. This results in increased electrostatic attraction, and more energy is required to remove the outer electron, increasing ionisation energy.

Question 24

What are the two exceptions to the 1st ionisation energy trend across a period.

(Ionisation Energies)

Answer 24

between groups 5 and 6, along with 2 and 3, where dips occur

Question 25

Explain the exception, between groups 5 and 6, to the 1st ionisation energy trend across periods. | (Ionisation Energies)

Answer 25

Sulfurs electron shares a 3p orbital, resulting in repulsion. This means it takes less energy remove the electron, compared to phosphorus which has no repulsion within its orbital. | (see back page of booklet if don't understand)

Question 26

Explain the exception, between groups 2 and 3, to the 1st ionisation energy trend across periods. | (Ionisation Energies)

Answer 26

Aluminiums electron is removed from a 3p orbital which is higher in energy than magnesiums 3s orbital. This means less energy is required to remove it. | (see back page of booklet if don't understand)

Question 27

Extras to look at:

Answer 27

- Successive Ionisation Energies