Atomic Structure

Question 1

What is fragmentation?

Answer 1

When a covalent bond breaks due to electron bombardment leaving an ion and an undetected molecule

Question 2

What does the tallest peak on a mass spectrum show?

Answer 2

The most stable ion

Question 3

What is a molecular ion?

Answer 3

A molecule that has been ionised but not broken up

Question 4

Why must a sample be in gaseous form in mass spectrum?

Answer 4

Molecules are spread out

Question 5

What is electrospray ionisation?

Answer 5

• sample dissolved in polar solvent (provides H+ ion)
  M + H+ -> MH+
• injected using a capillary needle to create a single beam
• put under high voltage (desolvation)

Question 6

What happens in the drift region of a mass spectrometer?

Answer 6

Same kinetic energy so speed is inversely proportional to mass (higher mass: charge, slower)

Question 7

What happens in the acceleration area of a mass spectrometer?

Answer 7

Ions are given the same kinetic energy by an electromagnetic field

Question 8

Why is a vacuum required in a mass spectrometer?

Answer 8

Air molecules would prevent ions reaching the detector

Question 9

What happens in the ionisation area of a mass spectrometer?

Answer 9

Atoms gain a 1+ charge due to electron bombardment or electrospray ionisation

Question 10

Why do isotopes have similar chemical properties?

Answer 10

They have the same number of electrons (only the mass has changed- number of neutrons)

Question 11

What is the relative mass of an electron?

Answer 11

1/1840

Question 12

Why don’t electrons in the same orbital repel?

Answer 12

They have opposite spins

Question 13

How many electrons are there in each S P D F?

Answer 13

S=2
P=6 (2X3)
D=10 (2X5)
F=14 (2X7)

Question 14

What are the S D P F blocks of the periodic table?

Answer 14

S= group 1 & 2 including helium
P= groups 3-7 excluding helium 
D= transition metals
F= lanthanides & actinides

Question 15

What does the farthest peak on the right of a mass spectrum show?

Answer 15

Molecular peak (Mr)

Question 16

Why is electrospray ionisation preferred for larger molecules?

Answer 16

It does it cause fragmentation

Question 17

How are ions detected in a mass spectrometer?

Answer 17

An electron is given back to the ion from the detector which induces a current to flow proportionate to the mass. A mass spectrum is produced

Question 18

How do you calculate relative abundance of isotopes?

Answer 18

Probability tree

Question 19

What are the trends in successive ionisation energies?

Answer 19

• energy required increases (due to greater positive charge and smaller mass)
• small increases between sub-shell
• big increases between shells

Question 19

The is the X ionisation energy?

Answer 19

The energy needed to remove 1 moles of electrons from 1 mole of gaseous atoms with an (X-1) positive charge

Question 20

What are the rules for filling orbitals?

Answer 20

1) lowest to highest energy (1S, 2S, 3S, 3P, 4S, 3D, 4P, 5S)

2) bus seat (single then double)