Atomic structure

Question 1

Define the term relative atomic mass?

Answer 1

Average mass of an atom of an element, which is relative to 1/12 of the mass of Carbon-12

Question 2

Define first ionisation energy?

Answer 2

Amount of energy needed to remove a mole of electrons from a mole of atoms, in a gaseous state

Question 3

What is happening to the radius across a period?

Answer 3

Shielding is the same, nuclear charge increases so stronger electrostatic attraction between nucleus + outermost electrons, radius decreases

Question 4

What is happening to the IE across a period?

Answer 4

Shielding is the same, nuclear charge increases so stronger electrostatic attraction between nucleus + outermost electrons, so more energy required to remove the outermost electron so IE increases

Question 5

What is happening to the IE down a group?

Answer 5

Shielding increases, less electrostatic attraction between nucleus + outermost electrons, so less energy required to remove the outermost electron so IE increases

Question 6

Which is smaller, Na+ or Mg?

Answer 6

Na+ ion has less shells
Its electron is closer to the nucleus + there’s less shielding
So the outer electrons are more strongly attracted to the nucleus

Question 7

Why is it necessary to ionise the mixture?

Answer 7

Acceleration + detection

Question 8

How are the ions accelerated?

Answer 8

Positive ions accelerate towards the negatively charged plate

Question 9

Why do the different ions separate in the flight tube?

Answer 9

Same kinetic energy, different velocities
Heavier particles travel slower

Question 10

Why is the inside of the machine a vacuum?

Answer 10

So there particles can’t interfere with the ion beam made from the sample

Question 11

How are the ions detected + how is their abundance measured?

Answer 11

Ions hit the detector + gain an electron
This generates a current proportional to the abundance

Question 12

Name the ionisation method when a particle gains a proton to form an ion?

Answer 12

Electrospray

Question 13

What are the 2 measurement made by the mass spectrometer?

Answer 13

M/Z ratio
Relative abundance

Question 14

How are ions formed via electron impact?

Answer 14

• Sample is vaporised
• High-energy electrons are fired at sample from an electron gun
• One electron is knocked off each particle

Question 15

How are ions formed via electrospray ionisation?

Answer 15

• Sample is dissolved in a volatile solvent
• Sample is injected through a needle at high voltage
• Sample is ionised by gaining a proton

Question 16

A mass spectrum shows the measurement of M/Z ratio + relative abundance. Which axis represents M/Z ratio?

Answer 16

X Axis

Question 17

Equation of the element P during electro spray ionisation?

Answer 17

P + H+ ——> PH+