1.1 Atomic Structure

Question 1

What does the atomic number tell us about an element?

Answer 1

Number of protons in an atom

Question 2

What is relative atomic mass ?

Answer 2

Average mass of isotopes of an element compared to 1/12th the mass of an atom of carbon 12

Question 3

What is an isotope?

Answer 3

Different forms of the same elements with a different number of neutrons

Question 4

Does 3s or 4s have a higher energy?

Answer 4

3d

Question 5

What is an orbital

Answer 5

Region around the nucleus that can old up to 2 electrons

Question 6

What would be the relationship between 2 electrons in the same orbital in terms of their spin?

Answer 6

Spin in opposite directions as they repel each other due to their negative charge

Question 7

Why does copper not fit the trend for electron configuration?

Answer 7

It only has one electron in its 4s orbital before filling 3d

1s2…..3p6,4s1,3d10

Question 8

What are the 2 types of ionisation for a mass spectrometer?

Answer 8

1. Electron Impact
2. Electrospray

Question 9

How does electron impact ionisation work?

Answer 9

1. Hot wire filament with current running through it emitting electrons.
2. Knocks off one electron from each particle to form 1+ions

Question 10

How does Electrospray Ionisation work?

Answer 10

1. The substance is dissolved in a volatile solvent (water or ethanol)
2. Injected through a fine hypodermic needle to make it an aerosol.
3. Needle is attached to a positive terminal of a high-voltage power supply
4. Particle pick up a proton form the solvent as they leave the needle producing HX+ ions

Question 11

When would you use electron impact for mass spec ionisation?

Answer 11

1. Organic or Inorganic molecules with a low formula mass
2. Used for substances with a higher molecular mass including biological molecules

Question 12

What are the 3 stages of ToF Mass spectrometry?

Answer 12

1. Acceleration
2. Ion Drift
3. Detection

Question 13

What happens during the acceleration stage of ToF?

Answer 13

Positive ions attracted towards a negatively charged plate.

Question 14

What happens during the ion drift stage of ToF?

Answer 14

1. Ions pass through a hole in a plate, form a beam with a constant kinetic energy, travel along a tube to a detector.
2. Time of flight is directly proportional to the square root of mass

Question 15

What happens during the detection stage of ToF?

Answer 15

1. Positive ions pick up electrons, current flows, m/z value and time of flight recorded.
2. Largest current from must abundant ions

Question 16

What is first ionisation energy?

Answer 16

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.