Atomic structure

Question 1

Relative Atomic mass (AR)

1.2 Mass number and isotopes

Answer 1

• Is the average mass of an atom on a scale where carbon-12 is 12

Question 2

Relative molecular mass, Mr

1.2 Mass number and isotopes

Answer 2

• the average mass of a molecule of an element on a scale where an atom of carbon-12 is 12

Question 3

Electron configuration

subshell S

1.3 Electron configuration

Answer 3

number of orbitals: 1
max amount of electrons : 1 x 2 = 2

Question 4

Electron configuration

subshell p

1.3 Electron configuration

Answer 4

number of orbitals: 3
max amount of electrons : 3 x 2 = 6

Question 5

Electron configuration

subshell d

1.3 Electron configuration

Answer 5

number of orbitals: 5
max amount of electrons : 5 x 2 = 10

Question 6

electron configuration

trends in electron configuration

1.3 Electron configuration

Answer 6

• the orbitals are filled in order of energy levels but: 4s is lower in energy than 3d
• electrons fill the lowest energy shells first
• 4s orbital is filled before the 3d and emptied first in ionisation. “first in, first out”

Question 7

electron configuration

Exceptions to electron configuration trends

1.3 Electron configuration

Answer 7

• Cr,chromium - 1s2 2s2 2p6 3s2 p6 4s1 3d5
• Cu,Copper - 1s2 2s2 2p6 3s2 p6 4s1 3d10

Question 8

Ionisation energy

Ionisation energy definition

1.3 Electron configuration

Answer 8

• The first ionisation energy of an element is the amount of energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions

Question 9

Ionisation energy

Factors that effect trends Ionisation energy

1.3 Electron configuration

Answer 9

• Atomic radius- the larger the nucleus the small the attraction felt by the outer electrons
• Nuclear charge- the higher the charge the greater the attraction
• Electron shielding or screening – inner electrons shield the positive charge of the nucleus from the outer shell electrons

Question 10

Ionisation energy

General trend across a period

1.3 Electron configuration

Answer 10

• general trend is for first ionisation energy to increase across periods
• as there is an increase in nuclear charge and similar shielding.
• This means there is a greater attraction between the nucleus and outer electron
• so more energy is required to remove 1 electron.

Question 11

ionisation energy

how can you identify an element using successive ionisation energies?

1.3 Electron configuration

Answer 11

• by looking at the jumps in energy between the successive ionisation energies
• lareger jumps indicate an electron being lost from a new sub-shell

Question 12

Time of flight mass spectrometry

steps ?

hint - 4 steps

1.2 Mass number and isotopes

Answer 12

1. Ionisation- electron impact or electrospray
2. Acceleration
3. Flight tube
4. Detection

Question 13

Time of flight mass spectrometry

ionisation - electron impact

steps, particle formed, equation, used for?

1.2 Mass number and isotopes

Answer 13

Electron impact:
* The sample is vaporised and high energy electrons are fired at it from
an electron gun (is a hot wire filament) with a current running through it that emits beam of high energy electrons
- This usually knocks off one electron from each particle forming ‘
a l+ ion.
X(g) + e- x (g) + 2e­
Used for:
- Used for low formula mass species
- Forms ions called the molecular ion

Question 14

Time of flight mass spectrometry

Ionisation - electrospray

steps, used for

1.2 Mass number and isotopes

Answer 14

Electrospray:
* ln electrospray ionisation, the sample is dissolved in a volatile solvent and through a fine needle that is connected to the positive terminal
of a high voltage supply.
- This produces tiny positively charged droplets that have gained a proton from the solvent .
- The solvent evaporates from the droplets into the vacuum and the droplets get smaller and smaller until they may contain no more than a single positively charged ion.

Used for:
- Used for low formula mass species
- Forms ions called the molecular ion

Question 15

Time of flight mass spectrometry

Acceleration

1.2 Mass number and isotopes

Answer 15

• The positive ions are amacted towards a negatively charged plate and accelerate towards it.
• Lighter ions and more highJy charged ions achieve a higher speed.
• use ke=1/2mv^2

Question 16

Time of flight mass spectrometry

flight tube

1.2 Mass number and isotopes

Answer 16

The ions pass through a hole in the negatively charged
plate. forming a beam and travel along a tube

Question 17

Time of flight mass spectrometry

detection

1.2 Mass number and isotopes

Answer 17

• When ions with the same charge arrive at the detector,
  the lighter ones are first as they have higher velocities. The flight times are recorded. The positive ions pick up an electron from the detector, which causes a current to flow.

analysis:
* size of current indicates the size of a sample

Question 18

how to calculate relative atomic mass from abundances

1.2 Mass number and isotopes

Answer 18

(isotopic mass x relative abundance) / sum of all abundances

eg (185x10) + (186x17) / (10+17)