Physical - 1.1 Atomic Structure

Question 1

What happens in acceleration (TOF)?

Answer 1

The second stage of TOF spectrometry. The positively charged ions are accelerated by an electric field so that they have the same kinetic energy.

Question 2

What is the atomic nucleus?

Answer 2

Positively charged object composed of protons and neutrons at the centre of every atom with electrons orbiting it.

Question 3

Define atomic number

Answer 3

The number of protons in the nucleus.

Question 4

What is electron impact ionisation?

Answer 4

Method of ionisation in TOF spectrometry. The sample is vapourised and an electron gun fires high energy electrons at it, causing an election to be knocked off each particle to produce 1+ ions.

Question 5

What is electrospray ionisation?

Answer 5

Method of ionisation in TOF spectrometry. The sample is dissolved and pushed through a fine nozzle at a high pressure. A high voltage is applied to it causing each particle to gain an H+ ion. The sample is then turned into a gas.

Question 6

Define first ionisation energy

Answer 6

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

Question 7

Define isotope

Answer 7

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

Question 8

Define mass number

Answer 8

The total number of protons and neutrons in the nucleus.

Question 9

Define second ionisation energy

Answer 9

The energy required to remove 1 mole of electrons from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.

Question 10

What is a TOF spectrometer?

Answer 10

A method of mass spectrometry where an ions m/z ratio is determined by a time of flight measurement. Consists of four stages: ionisation, acceleration, in drift, and detection.

Question 11

What is an electron configuration?

Answer 11

The distribution of electrons of an atom in orbitals.

Question 12

What happens in ion detection?

Answer 12

Fourth stage of TOF spectrometry. The negatively charged plate detect charged particles and a mass spectrum is produced.

Question 13

What happens in ion drift?

Answer 13

The third stage of TOF spectrometry. The ions enter region with no electric field so they drift through it. The light of the ion, the faster they will drift.

Question 14

What happens in ionisation (TOF)

Answer 14

First stage of TOF. The sample can be ionised by electro spray ionisation or electron impact ionisation.

Question 15

What did the plum pudding model represent?

Answer 15

It represented atoms as a sphere of positive charge, with small negative charges distributed evenly within it

Question 16

What is the electron shell model (Rutherford)?

Answer 16

The atom consists of a small, dense central nucleus surrounded by orbiting electrons in electron shells

Question 17

What is the relative charge and mass of a proton?

Answer 17

Relative charge = +1
Relative mass = 1

Question 18

What is the relative charge and mass of a neutron?

Answer 18

Relative charge = 0
Relative mass = 1

Question 19

What is the relative charge and mass of an electron?

Answer 19

Relative charge = -1
Relative mass = 1/1840

Question 20

What is the mass number a sum of?

Answer 20

The sum of protons and neutrons in an atom

Question 21

What is atomic number equal to?

Answer 21

The number of protons

Question 22

What happens in ionisation (TOF)?

Answer 22

A sample of an element is vaporised and injected into the mass spectrometer where a high voltage is passed over the chamber. This causes electrons to be removed from the atoms leaving +1 charged ions in the chamber.

Question 23

What happens in acceleration (TOF)?

Answer 23

These positively charged ions are then accelerated towards a negatively charged detection plate

Question 24

What happens in acceleration (TOF)?

Answer 24

These positively charged ions are then accelerated towards a negatively charged detection plate

Question 25

What happens in ion drift (TOF)?

Answer 25

The ions are deflected by magnetic field into curved path. The radius of their path is dependent on the charge and mass of the ion.

Question 26

What happens in detection (TOF)?

Answer 26

When the positive ions hit the negatively charged detection plate, they gain an electron producing a flow of charge. The greater the abundance, the greater the current produced.

Question 27

What happens in analysis (TOF)?

Answer 27

These current values are then used in combination with the flight times to produce a spectrum printout with the relative abundance of each isotope displayed

Question 28

What is the equation for relative atomic mass using a spectra?

Answer 28

Ar = (m/z x abundance) / (total abundance)

Question 29

How many electrons can be held in the S orbital?

Answer 29

Two

Question 30

How many electrons can be held in the P orbital?

Answer 30

Six

Question 31

How many electrons can be held in the D orbital?

Answer 31

10

Question 32

What are the three rules for writing out electron configurations?

Answer 32

1) the lowest energy orbital is filled first
2) electrons with the same spin fill up and orbital first before pairing begins
3) no single orbital holds more than two electrons

Question 33

Define ionisation energy

Answer 33

The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state

Question 34

What is the trend in first ionisation energy along a period?

Answer 34

First ionisation energy increases due to decreasing atomic radius and greater electrostatic forces of attraction

Question 35

What is the trend in first ionisation energy down a group?

Answer 35

First ionisation energy decreases due to an increasing atomic radius and shielding which reduces the effect of the electrostatic forces of attraction

Question 36

Why is the first ionisation energy of aluminium lower than expected?

Answer 36

Due to a single pair of electrons with opposite spin. As a result, there is a natural repulsion which reduces the amount of energy needed to be put in to remove the outer electron.