Atomic structure Flashcards
Relative Atomic mass (AR)
- Is the average mass of an atom on a scale where carbon-12 is 12
Relative molecular mass, Mr
- the average mass of a molecule of an element on a scale where an atom of carbon-12 is 12
Electron configuration
subshell S
number of orbitals: 1
max amount of electrons : 1 x 2 = 2
Electron configuration
subshell p
number of orbitals: 3
max amount of electrons : 3 x 2 = 6
Electron configuration
subshell d
number of orbitals: 5
max amount of electrons : 5 x 2 = 10
electron configuration
trends in electron configuration
- the orbitals are filled in order of energy levels but: 4s is lower in energy than 3d
- electrons fill the lowest energy shells first
- 4s orbital is filled before the 3d and emptied first in ionisation. “first in, first out”
electron configuration
Exceptions to electron configuration trends
- Cr,chromium - 1s2 2s2 2p6 3s2 p6 4s1 3d5
- Cu,Copper - 1s2 2s2 2p6 3s2 p6 4s1 3d10
Ionisation energy
Ionisation energy definition
- The first ionisation energy of an element is the amount of energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions
Ionisation energy
Factors that effect trends Ionisation energy
- Atomic radius- the larger the nucleus the small the attraction felt by the outer electrons
- Nuclear charge- the higher the charge the greater the attraction
- Electron shielding or screening – inner electrons shield the positive charge of the nucleus from the outer shell electrons
Ionisation energy
General trend across a period
- general trend is for first ionisation energy to increase across periods
- as there is an increase in nuclear charge and similar shielding.
- This means there is a greater attraction between the nucleus and outer electron
- so more energy is required to remove 1 electron.
ionisation energy
how can you identify an element using successive ionisation energies?
- by looking at the jumps in energy between the successive ionisation energies
- lareger jumps indicate an electron being lost from a new sub-shell
Time of flight mass spectrometry
steps ?
hint - 4 steps
- Ionisation- electron impact or electrospray
- Acceleration
- Flight tube
- Detection
Time of flight mass spectrometry
ionisation - electron impact
steps, particle formed, equation, used for?
Electron impact:
* The sample is vaporised and high energy electrons are fired at it from
an electron gun (is a hot wire filament) with a current running through it that emits beam of high energy electrons
- This usually knocks off one electron from each particle forming ‘
a l+ ion.
X(g) + e- x (g) + 2e
Used for:
- Used for low formula mass species
- Forms ions called the molecular ion
Time of flight mass spectrometry
Ionisation - electrospray
steps, used for
Electrospray:
* ln electrospray ionisation, the sample is dissolved in a volatile solvent and through a fine needle that is connected to the positive terminal
of a high voltage supply.
- This produces tiny positively charged droplets that have gained a proton from the solvent .
- The solvent evaporates from the droplets into the vacuum and the droplets get smaller and smaller until they may contain no more than a single positively charged ion.
Used for:
- Used for low formula mass species
- Forms ions called the molecular ion
Time of flight mass spectrometry
Acceleration
- The positive ions are amacted towards a negatively charged plate and accelerate towards it.
- Lighter ions and more highJy charged ions achieve a higher speed.
- use ke=1/2mv^2
