Atomic Structure

What is relative atomic mass? (2)

The average mass of an atom of an element, compared to 1/12 the mass of an atom of carbon-12

How are molecules ionised using electrospray ionisation

sample is dissolved in a volatile solution, injected through a needle at a high voltage, each molecule gains a proton forming MH+

What is the general trend of Ionisation Energy along a period? (5)

1st IE increases, more protons so higher nuclear charge, electrons in the same energy level, so shielding is similar, stronger attraction between nucleus and outer e as they are closer

What is the first exception to ionisation energy trend along a period? (4)

group 2-3, group 3 lower than group 2, outer electron is in P orbital, P orbital is higher in energy than S orbital. So there is a large jump in ionisation energy

what is the second exception to ionisation energy across a period? (4)

group 5-6, group 6 lower, 2 electrons in P orbital are paired, pairing causes electron to electron repulsion. So there is a large jump in ionisation energy.

how are atoms ionised using electron impact ionisation? (3)

sample is vapourised, an electron gun bombards the ion using high energy electrons, each molecule loses an electron forming M+

Outline how TOF mass spec can separate two species (4)

positive ions are accelerated using an electric field, to the same kinetic energy, lighter mass species will travel faster, therefore the lighter mass species will be detected first 

state how relative abundance is determined in a TOF mass spec

The number of ions that hit the detector and gain an electron at the same time. Relative abundance depends on the size of the current. Current is proportional to relative abundance

mass of an electron

1/1840

why is ionisation energy higher in innermore shells?

electron in higher energy level, less shielding, more energy required to remove as stronger attraction between electron and nucleus

why is first ionisation energy decreases down group

more shielding as more electron shells, weaker attraction between outer electron and nucleus, easier to remove