the sub-atomic particles are protons and neutrons in the nucleus, and electronsorbiting in energy shells
relative masses of sub-atomic particles:
electron = 1/1840
proton = 1
neutron = 1
relative charges of sub-atomic particles:
electron = -1
proton = +1
neutron = 0
atomic number is the number of protons in the nucleus of an atom
atomic number is represented by Z
mass number is the number of protons and neutrons in the nucleus of an atom
mass number is represented by A
isotopes are two atoms with the same number of protons and electrons but a different number of neutrons
isotopes react in the exact same way chemically
electrons orbit the nucleus of an atom and are held in electron shells which increase in energy the further you get from the nucleus
electrons can behave as a particle, wave or cloud of charge
the first shell holds up to 2 electrons, the second shell holds up to 8 electrons and the third shell holds up to 18 electrons
a mass spectrometer is an instrument which can be used to determine the relative atomic mass of a sample
there are many types of mass spectrometry but all are based on forming ions and separating the ions based on their charge:mass ratio
time-of-flight spectrometry records the time taken for ions to reach a detector and uses this to identify them
TOF spectrometry has the following stages:
ionisation
acceleration
ion drift
detection
analysis
in the first stage of TOF spectrometry, ionisation, the sample is vaporised and injected into the chamber
the two types of ionisation in TOF spectrometry are electron bombardment, where ions lose an electron, and electrospray, where ions gain a proton, both create 1+ ions
in the second stage of TOF spectrometry, acceleration, the molecules are given energy so they all have the same kinetic energy, then accelerated towards a negative plate
in the third stage of TOF spectrometry, ion drift, ions are deflected by a magnetic field so travel in a curved path, depending on their charge and mass
in the fourth stage of TOF spectrometry, detection, positive ions hit negative plate, they gain an electron, this causes a current to flow, greater abundance = greater current
in the fifth stage of TOF spectrometry, analysis, current values are used in combination with flight times to produce a mass spectrum
mass spectra are produced from a mass spectrometer, they show the abundance of different ions separated by their mass/charge ratio
energy levels are divided into sub-levels, named s, p, d and f
different orbitals have different energies depending on the energy level they are in
the atomic orbitals of each main level have different shapes with different energies, these are the sub-levels, they represent a volume of space where there is a 95% chance of finding an electron
s-orbitals can hold up to 2 electrons
p-orbitals can hold up to 2 electrons each, but come in groups of 3 so 6 electrons in the sub-level
d-orbitals can hold up to 2 electrons each, but come in groups of 5 so 10 electrons in the sub-level
electron configuration is written in the form 1s22s22p63s23p63d104s24p6 and so on
the 4s orbital is filled before the 3d orbital because it is of lower energy
the electron configuration of chromium is 1s2 2s2 2p6 3s2 3p6 4s1 3d5
ionisation energy is the minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state
first IE is shown by the equation:
M(g)→M+(g)+e−
second IE is shown by the equation:
M+(g)→M(g)2++e−
third IE is shown by the equation:
M(g)2+→M(g)3++e−
along a period, first IE increases due to decreasing atomic radius and increasing electrostatic forces of attraction
down a group, first IE decreases due to increasing shielding and increasing atomic radius
electrospray ionisation of X process:
X is dissolved in a solvent
X is injected through a needle at high voltage
it gains a proton
the equation is X + H+ -> XH+
remember which type of ionisation is which because electrospray ionisation has a p in it so a proton is gained, and electron bombardment has an e in it so an electron is lost
electron bombardment is the same as electron impact