Fundamental particles and ionisation energy

Mass spectrometery

Measures relative atomic mass and frequency of different isotopes

The sample is vaporised and ionised

The ions are separated according to their charge and mass

Mass spectrometry steps

Samples of unknown substances are ionised to form positive ions by electron impact

The positive ions are accelerated by an electric field. Lighter ions will accelerate greater

The ions drift with no electric field at the same speed they were travelling

Lighter ions hit the detector first than heavier ions, creating an electric current

Relative atomic mass equation in mass spec

relative abundance of each isotope x relative mass of each isotope

Total abundance

Relative atomic mass

The weighted average mass of an atom of en element with its naturally occurring isotopes compared to 1/12 the relative atomic mass of carbon 12

Relative isotopic mass

The mass of an individual atom of a particular isotope relative to 1/12 the relative atomic mass of carbon 12

Electrons in shell

2n² where n=number of shells

-Lowest energy orbital is filled first. Order of filling is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p

-Electron with the same spin fill up an orbital first before pairing begins

-No atomic orbital can hold more than 2 electrons. When two electrons do exist in the same orbital, they must be of opposite spin

S-orbitals

Orbitals are regions of space where electrons are most likely to be in

S-orbitals is the first orbital, can hold up to 2 electrons

P-orbitals

P sublevels can have 3 P-orbitals which can take 3 pairs of electrons, total of 6 electrons

Up to 2 electrons can exist in each orbitals

D-orbitals

D sublevel has 5 orbitals and take a maximum of 10 electrons

Up to 2 electrons can exist in each orbital

First ionisation energy

The minimum energy required to remove one mole of electrons from one mole of gaseous atoms.

Always endothermic because energy is required to overcome the attraction between the positively charged nucleus and negatively charged electron

Trends of first ionisation energy

Increases across a period because the number of protons increases, increasing nuclear charge. Shielding remains approximately constant because electrons are added to the same principal energy level. The atomic radius decreases, so there is stronger attraction between the nucleus and the outer electron.

Decreases down a group due to atomic radius increasing because the number of occupied electron shells increases. Electron shielding increases due to additional inner electron shells.The electrostatic attraction between the nucleus and outermost electron decreases.

Fall between group 2 and 3

First ionisation energy of aluminium is lower than expected because in magnesium, the outer electron is removed from the 3s subshell, whereas in aluminium it is removed from the higher-energy 3p subshell. The 3p electron is easier to remove, so aluminium has a lower first ionisation energy.

Fall between group 5 and 6

First ionisation energy of sulfur is lower than expected because there is repulsion between its pair of electrons which makes it easier to remove one of them, less energy is required

Boron has lower first ionisation energy than beryllium…

Boron’s outer electron occupies a 2p subshell, whereas beryllium’s occupies a 2s subshell

2p subshell has a higher energy level than 2s subshell

Boron’s outer electron experiences less electrostatic force of attraction to the nucleus, so less energy is required to remove it

Successive ionisation energy

The energies required to remove electrons one at a time from an atom or ion in its gaseous state. This requires more energy because the electrostatic force of attraction between the positive nucleus and the negative outer electron increase, so more energy is needed to overcome this attraction

Successive ionisation energy increases because

An electron is removed, making the ion more positively charged

Number of protons stays the same

The remaining electrons experience a stronger electrostatic attraction to the nucleus

More energy is required to remove the next electron

Large jumps in successive ionisation energy

Occurs when an electron is removed from an inner shell

Electrons in inner shell experience less shielding from other electrons so are more strongly attracted to the nucleu which requires more energy to do so

The number of electrons removed before the first large jump tells you how many electrons are in the outer shell