Atomic Structure

Question 1

whats the difference between rutherford’s model of the atom and the current model

Answer 1

• in the current model the nucleus contains neutrons and protons
• the current model has electron in multiple orbitals/subshells, unlike all in one orbital like in the old model.

Question 2

define the mass number

Answer 2

the number of protons and neutrons in the nucleus.

Question 3

define the relative atomic mass

Answer 3

the average mass of an atom of an element compared to a carbon 12 atom.

Question 4

Give two reasons why it is necessary to ionise the isotopes of of an element before they can be analysed in a TOF mass spectrometer.

Answer 4

1. The ions can be accelerated towards a negative plate.
2. The ions can be detected by creating a current when they hit the detector.

Question 5

How are molecules ionised by electrospray ionisation

Answer 5

the molecules dissolved in a volatile substance which is then injected through a fine hyperdermic needle to give off a fine mist, here they gain a H+ ion and are attracted towards the negative plate.

Question 6

How are molecules ionised by electron gun ionisation

Answer 6

A vapourised sample of the molecules is injected at low pressure. then an electron gun with a high voltage current flowing through it, emits electrons at the samples. this knocks off electrons from the moecules and they become 1+ ions which are attracted to the negative terminal.