Chem 1 - Atomic structure

Question 1

What’s the relative atomic mass?

Answer 1

The average mass of an atom taking into account all isotopes

Question 2

What are orbitals?

Answer 2

Regions of space that electrons are most likely to be in

Question 3

What groups are in the S block?

Answer 3

Group 1 and 2

Question 4

What groups are in the D block?

Answer 4

Transition metals

Question 5

What groups are in the P block?

Answer 5

Group 3-7

Question 6

List the two things mass spectrometry can be used?

Answer 6

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

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

Question 7

What happens in Time Of Flight (TOF) mass spectrometry?

Answer 7

Particles of the substances are ionised to form 1+ ions which are accelerated so that they all have the same kinetic energy.

Question 8

What is mr?

Answer 8

The average mass of a molecule compared to an atom of C -12

Question 9

What happens in stage 1: ionisation of TOF mass spectrometry (electron impact)

Answer 9

1. High energy electrons are fired from an electron gun which is a hot wire filament with a current running through it
2. An electron is knocked off to leave a + ion

Question 10

What happens in stage 1: ionisation of TOF mass spectrometry (dissolved in a volatile solvent)

Answer 10

1. Forced through a hollow needle that is connected to a + terminal of a high voltage supply
2. Produces tiny + droplets that have lost electrons to the + charge of supply
3. The solvent evaporates from droplets into a vacuum until one + ion is left

Question 11

What happens in stage 2: Acceleration of TOF mass spectrometry?

Answer 11

1. All ions have some kinetic energy
2. The positive ions are attracted towards a negatively charged plate and they accelerate towards it
3. lighter ions and more highly charged ions have a higher speed

Question 12

What happens in stage 3: Flight tube of TOF mass spectrometry.

Answer 12

1. Ions pass into a tube through the negatively charged plate hole
2. They all have the same KE but TOF depends on velocity which depends on its mass

Question 13

Explain how you can work out the relative atomic mass from a mass spectrum (3 marks)

Answer 13

1) For each peak, read the % relative isotopic abundance from the y-axis and the relative isotopic mass from the x-axis. Multiply them together to get the total mass for each isotope
2) Add up these totals
3) Divide by 100 because percentages were used

Question 14

What is the definition of the first ionisation energy?

Answer 14

The first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to from 1 mole of gaseous 1+ ions.

Question 15

How do you write an equation for ionisation?

Answer 15

X(g) —> X+(g) + e-

Question 16

If the ionisation energy is low what happens?

Answer 16

Its easier to form an ion.

Question 17

List the 3 things that effect ionisation energies?

Answer 17

1) Nuclear charge
2) Distance from nucleus
3) Shielding

Question 18

What is shielding?

Answer 18

As the number of electrons between the outer electrons and the nucleus increases the outer electrons feel less attraction towards the nuclear charge. This lessening of the pull of the nucleus by inner shells of electrons is called shielding.