Name the subatomic particles including charge and mass
proton; charge 1, mass 1 neutron; charge 0, mass 1 electron; mass 1/1836, charge -1
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Define mass number
mass of an atom (protons and neutrons)
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Define atomic number
number of protons (and electrons) in an atom
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How are ions formed?
losing or gaining electrons
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Define isotope
atoms of the same element (same number of protons and electrons) but a different number of neutrons
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What was the atomic model by the greek philosophers?
all matter consisted of smaller building blocks. (beginnings of atom)
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What did JJThomson believe about the atom?
negative corpuseles were suspended in a sea of positive charge and that atoms had no empty space. It was known as the plum pudding model.
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What did Ernest Rutherord discover about the atom?
positive matter is concentrated in the centre and negative charge orbits the outside. (gold sheet alpha particles experiment)
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What extra did Neils Bohr add to the atom model?
orbitals
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What is the quantum mechanics model of the atom
electrons are both waves and particles and in this model we can predict electron movement
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How does electron impact ionisation work? include a half equation
-high energy electron fired at sample from electron gun -an outer electron is knocked off the atom forming a 1+ ion - Cl(g) arrow Cl+(g) + e-
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how does eletrospray ionisation work?
-sample dissolved in volatile solvent - sample is injected through a fine needle to give a fine mist - tip of the needle is attched to a positive terminal of high voltage supply - partilce gains H+ ion from solvent - XH+ ion formed
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Why must you ionise molecules in mass spectrometry?
- only ions interact with and be accelerated by the electric field - only ions will create a current when hitting the dectector
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How are ions seperated in a TOF mass spectrometer?
- positive ions accelerated by an electric field to a constant kinetic energy -ions with smaller m/z have same kinetic energy as those woth greater m/z so smaller ones travel faster - ions with smaller m/z arrive at the detector first
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How is abundance measured in a TOF mass spectrometer?
-ions hit negative plate of detector and ion accepts an electron causing a current - size of current is proportional to abundance of isotope
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What can sometimes happen in electron impact ionisation?
molecules fragment
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Give the formula for average relative atomic mass
total(massxabundance) / total abundance
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If an isotope of mass 10 has an abundance of 23 and isotope mass 11 has an abundance of 100 what is the relative atomic mass?
10.8
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What two combined formulas give TOF?
KE = 1/2 mv2 V=d/t so d/t = squareroot(2KE/m)
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KE=1.1x10-3 J T=1.07x10-6 s m= 60g work out distance(d)
1.59m
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In what order are the orbitals?
1s 2s 2p 3s 3p 4s 3d 4p etc
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Which two elements have strange electron arrangements and why?
copper and chromium because an electron moves from 4s orbital to complete a row in 3d orbital
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How do you work out ion electron configuration?
Add or take electrons from subshells in order except from the 4s and 3d subshell in which 4s is removed first
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What is ionisation energy?
the energy required to remove a mole of electrons from a mole of atoms in the gaseous state
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what happens to ionisation energy as each successive electron is removed?
each electron requires more energy than the last but there is a significant change when the first electron is removed from a new principle energy level
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What happens to ionisation energies down a group?
outer electrons are further from the nucleus so have more shielding and therefore the elements lower in the group have lower ionisation energies
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What happens as you go across a period?
the atomic radius decreases and proton number increases so positive charge increases and therefore ionisation energy increases
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What causes dips and decreases in ionisation energy across a period?
when a new subshell/orbital is reached due to increased shielding and when all single electrons begin to form pairs due to electron replusion making it easier to remove electrons
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Summarise the factors affecting ionisation energy
major factors; strength of nuclear charge (proton increases), atomic radius, shielding minor factors; paring of electron (repulsion), new subshell (minor shielding)
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