Atomic Structure

Question 1

Why do elements need to be ionised?

Answer 1

• so it can be accelerated through the electric field
• so it can be detected at the end by the ion detector

Question 2

Relative atomic mass

Answer 2

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 3

Relative molecular mass

Answer 3

The weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12.

Question 4

Explain why isotopes of the same element have the same chemical properties

Answer 4

Isotopes have the same electron configuration

Question 5

first ionisation energy

Answer 5

Energy needed to remove 1 mole of electron from one mole of atom in the gaseous state to form 1 mole of gaseous ion

Na(g) —> Na+(g) + e-

Question 6

Second ionisation energy

Answer 6

Na+(g) —> Na2+(g) + e-

Question 7

Why are successive ionisation energies always larger?

Answer 7

• The second ionisation energy of an element is always bigger than the first ionisation energy.
• When the first electron is removed a positive ion is formed.
  -The ion increases the attraction on the remaining electrons and so the energy required to remove the next electron is larger.

Question 8

Explain why fluoride ion is larger than a sodium ion.

Answer 8

• They both have the same number of electrons,
• but Sodium ion has a higher proton number
• so a higher nuclear charge (meaning the electrons will be pulled in greater, making the atomic radius of Sodium decrease.)

Question 9

Explain how ions are detected and relative abundance is measured in a TOF mass spectrometer (2)

Answer 9

• ions hit the detector and gain a electron
• relative abundance is proportional to the size of current

Question 10

State the trend in the atomic radius of the elements down group 2
Give a reason for this trend (2)

Answer 10

• Increases
• The number of electron energy levels increases

Question 11

Explain why the second ionisation energy of magnesium is greater than the first ionisation energy of magnesium.

Answer 11

• Electron being removed from a positive ion (therefore need more energy)/ electron being removed is closer to the nucleus

Question 12

Explain why the ionisation energy of every element is endothermic.

Answer 12

Heat or energy needed to overcome the attraction between the (negative) electron and the (positive) nucleus or protons