Topic 1- Atomic Structure and the Periodic Table

Question 1

1.1- what is the structure of an atom in terms of electrons, protons and neutrons

Answer 1

ELECTRONS- whizz around the nucleus in ORBITALS (take up most volume of the atom).

PROTONS+NEUTRONS- in the nucleus with most of the mass being concentrated

Question 2

1.2- know the relative mass and relative charge for protons, neutrons and electrons

Answer 2

Proton: RM- 1
RC- 1+
Neutron: RM- 1
RC- 0
Electron: RM- 0.0005
RC- 1-

Question 3

1.3- what is meant by ‘atomic number’ and ‘mass number’

Answer 3

ATOMIC- number of PROTONS in the nucleus, atoms of the same element= same no of protons

MASS- TOTAL no of protons and neutrons

Question 4

1.5- what is meant by isotopes

Answer 4

atoms with the same number of protons but different number of neutrons

Question 5

1.6- define ‘relative atomic mass’ and ‘relative isotopic mass’

Answer 5

RAM- weighted MEAN MASS of an atom of an element, compared to 1/12th of the mass of an atom of carbon-12.

RIM- mass of an atom of an ISOTOPE compared with 1/12th of the mass of an atom of carbon-12.

Question 6

1.7- what is meant by ‘relative molecular mass’ (also known as ‘relative formula mass’)

Answer 6

RELATIVE MOLECULAR MASS
- refers to simple molecules
- just ADD up the RAM values of all atoms in the molecule

RELATIVE FORMULA MASS
- used for compounds that are ionic or giant covalent
- ADD up the RAM of all the ions or atoms in the formula unit

Question 7

1.8- how do you analyse and interpret data from mass spectrometry to calculate RAM from relative abundance of isotopes

Answer 7

if the isotopic abundances are in percentages….

1. MULTIPLY each relative isotopic mass by % relative isotopic abundance, and ADD up the results.
2. DIVIDE by 100

Question 8

1.9- be able to predict the mass spectra, including relative peak heights, for diatomic molecules, including chlorine

Answer 8

mass spectra- used to work out the RAM of different elements
- y-axis: abundance of ions (relative isotopic abundance)
- x-axis: relative isotopic mass (m/z- mass/ charge)

Method:
1. MULTIPLY relative isotopic mass by relative isotopic abundance, add up results
2. Divide by the sum of the isotopic abundances.

Question 9

1.10- understand how mass spectrometry can be used to determine the relative
molecular mass of a molecule

Answer 9

1- Express each of the percentages as a decimal e.g. 75%= 0.75
2- Multiply abundances of the isotopes to get the relative abundance of each one.
3- Any molecules that are the same -> add uptheir abundances (e.g. Cl35- Cl37 and Cl37-Cl35 are the same so 0.1875+0.1875= 0.375)
4- Divide all the relative abundances by the smallest relative abundances to get the smallest whole number ratio and by working out the relative molecular mass, you can predict the mass spectrum.

Question 10

1.11- define ‘first ionisation energy’ and ‘successive ionisation energy’

Answer 10

‘first ionisation energy’= energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms (to form 1 mole of gaseous 1+ ions)
‘successive ionisation energy’=