Unit 1 Chemistry

Proton Neutron Electron
Relative Mass 1 1 1/1840
Relative Charge +1 0 -1

The protons and neutrons are in the centre of the atom, held together by a force called the strong nucleur force, which is much stronger than the electrostatic forces that hold the electrons and protons together in the atom. It overcomes the repulsion between the proton in the nucleus.

Carbon - 2,4
Sulfur - 2,8,6
Sodium Ion - 2,8

Where the proton and therefore electron number are the same, but where the neutron number varies. The ones that vary are called isotopes. They react chemically in the same way, however they vary in mass number due to the difference in neutrons.

Deutrium = hydrogen-2 p-1,e-1,n-1
Titrium = hyrdrogen-3 p-1,e-1,n-2

IONISATION: The electron gun knocks out electrons out of atoms or molecules to form positive ions. Most lose just one electron so become +1, 5% become +2 though.
ACCELERATION: The positive ions are attracted to the negatively charged plates. The lighter ions accalerate at a faster speed. Some ions pass through the slits in the plates, so the ions are in a beam
DEFLECTION: The beam of ions travel into a magnetic field and deflect them into an arc of a circle. The deflection depends on the mass/charge ratio (m/z) - z is usually +1. The stronger the magnetic field strength, the greater the deflection
DETECTION: The magnetic field is gradually increased so the ions of increasing mass enter the detector one after another. They hit the detector , accept electrons, lose their charge and create a current proportional to the abundance of each ion.

Its used to identify the different isotopes in an element. It detects individual ions, so different isotopes are detected differently due the difference in masses.
high resolution mass - measure the relative atomic mass to 5.d.p
low resolution mass - nearest whole number

(90 x 20) + (10 x 22)
---------------------------- = 20.2
100