atomic structure 3.1.1 in papers 1 & 3

• Dalton atoms are indivisible, atoms of each element have different masses. • Thomson atom is positively charged sphere embedded with negative electrons. • Rutherford the mass of the atom is concentrated is a tiny positively charged center. • Bohr electrons have fixed energy levels • Shrondinger electrons are found in orbitals.

• atoms with the same number of protons, but different numbers of neutrons. • they have similar chemical properties because they have the same shell structure. • they may have slightly varying physical properties due to the different masses.

A powerful instrumental method of analysis that can be used to: - find the abundance and mass of each isotope in an element allowing us to determine its relative atomic mass. - find the molecular atomic mass of substances made of molecules.

• electron impact ionisation (gun method) • electrospray ionisation

• the sample is vapourised and fired with high energy electrons from an electron gun which knocks of 1 electron from each particle. • the ions formed are attracted towards a negative plate where they are accelerated.

• the sample is dissolved in a volatile solvent and injected through a fine needle to give a fine mist. • the tip of the needle is attached to the positive terminal of high voltage power supply. • the particles are ionised by gaining a proton (H+) from solvent as they leave the needle.

• X (g) + e -> X+ (g) + 2e • elements • substances made of molecules with a low molecular mass. • however molecules often fragment.

• X(g) + H+ -> XH+(g) • substances made of molecules with a high molecular mass, including biological ones (proteins). • molecules rarely fragment. • resulting ions have a Mr one unit higher due to gain of protons. • cant be used if particles arent capable o gaining a proton.

• acceleration • positive ions are accelerated using an electron field so that they all have the same kentetic energy. • KE = joules • mass = KG • given particles have the same kenetic energy, the velocity of each one depends on its mass, lighter ones are faster.

• flight tube • the positive ions travel through a hole in the negatively charged plate into a tube. • the time of flight depends on velocity which depends on mass. • v=d divided by t

• detection • the postive ions hit a negatively charged electric plate. • the ions reach the detector and generate a small current, which is fed to a computer for analysis. • the current is produced by electrons transferring from the detector to the positive ion. • the size of the current is proportional to the abundance of the species. • the size of the current gives a measure of the number of ions hitting the plate.

• data analysis • a computer uses the data to produce a mass spectrum. • shows mass of the ion.

total mass of each isotope —————————-. total abundance

R.A.M = (isotopic mass x relative abundance) —————————-. total relative abundance

• furthest to the right of the significant peaks = molecular ion peak. • mass/charge = Mr of the molecule. • other peaks are fragments you ignore.

mass = Ar/L

v = 2KE -.—– m square root it

d = vt (need to work out mass then velocity then distance).

• principle (main shell, assigned numbers, 1,2,3 etc) • subsidary ( orbitals, assigned letters s,p,d,f etc)

s level - 2 p level (3 types) - 6 d level (5 types) - 10 f level (7 types) - 14

• a 3D region of space where an electron is found. • can hold 2 electrons but will have opposite spin to overcome the repulsion between them.

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10 etc. - lower energy orbitals are filled first.

Cr- 1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1 Cu- 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1

• the energy required to remove a mole of electrons from a mole of atoms in the gaseous state. • used only for positive ions. • first ionisation: H(g) -> H+(g) + e- • second ionisation: : Ti+(g) -> Ti2+(g) + e-