diatomic molecules in mass spectrometers and ionisation energy

Question 1

why do some diatomic molecules fragment in mass spectrometers

Answer 1

some molecules fragment due to electron impact ionisation

Question 2

write an equation for 79Br and 81Br that fragments

Answer 2

79Br 81Br —> 79Br+ 81Br+ +2e-

(forms 2 positive ions)

Question 3

write an equation for 79Br and 81Br that doesn’t fragment

Answer 3

79Br 81Br —> 79Br+ +e-

(forms 1 positive ion)

Question 4

define ionisation energy

Answer 4

ionisation energy is the amount of energy needed to convert 1 mole of gaseous atoms into 1 mole of gaseous ions with a positive charge

Question 5

write the equation for ionisation energy

Answer 5

X (g) —> X+ (g) + e-

Question 6

what factors control the strength of attraction and therefore the ionisation energy

Answer 6

• distance
• value of the charge

Question 7

across a period why does the electrostatic pull by the nucleus on the outer electron shell increase?

Answer 7

across a period the nuclear change is increasing

Electron shielding (by inner shells) is staying constant

This means the effective nuclear charge increases

The electrostatic pull by the nucleus on the outer electron shell therefore increases

Question 8

show the 3 first successive ionisation energies of Na

Answer 8

Na (g) —> Na+ (g) + e-

Na+ (g) —> Na2+ (g) + e-

Na2+ (g) —> Na3+ (g) + e-