ATOMIC STRUCTURE Flashcards
Lost the 3 sub atomic particles
Proton
Neutron
Electron
What is the relative mass of an electron
1/1840
Define atomic number
The number of protons in the nucleus
Define mass number
The number of protons and neutrons in the atom
Define isotope
Atoms with the same number of protons but different numbers of neutrons
Outline the features of isotopes
Similar chemical properties
Due to same electronic structure
Slightly varying physical properties
Due to different masses
Define the use of a time of flight mass spectrometer
Determine I stopped present in a sample of an element
Identify elements
Calculate relative atomic mass
What are the 4 steps in a mass spectrometer
Ionisation
Acceleration
Flight tube
Detection
Outline electron impact ionisation
Vapour used sample injected at low pressure
Electron gun fires high energy electrons at sample
Outer electron is knocked out
Positive ion is formed with different charges
When is electron impact used?
Elements and substances with low formula mass
As larger organic molecules can fragment
Outline electro spray ionisation
Dissolve sample in volatile polar solvent
Object through hypodermic needle giving fine mist or aerosol with high voltage
Sample molecule gains proton and H+
Solvent evaporates and negative sample H+ ions move toward negative plate
When is electro spray ionisation used
Larger organic molecules
Softer conditions prevent fragmentation
Outline acceleration in TofF mass spectrometry
Positive ions are accelerated
By an electric field
To a constant kinetic energy
Why are ions accelerated in TofF spectrometry
Same kinetic energy
Different mass
Velocity depends on mass
Lighter particles have faster velocity
Heavier particles have slower velocity
Outline what happens in the flight tube
Positive ions with smaller m/z have same kinetic energy as larger m/z
So they move faster
Heavier particles take longer in the drift area
Ions are distinguished by different flight times
Outline detection in a TofF mass spectrometer
Ions generate small current at detector plate
Linked to computer for analysis
Current is proportional to abundance of species
Due to electron transfer to ions
What can a mass spectrometer measure
M/z (mass to charge ratio)
Abundance
What happens if two electrons are removed
Halves the mass value
Due to m/z ratio
Outline the equation for calculating relative atomic mass
from percentage abundance
(Sum of) isotopic mass x % abundance
all over 100(%)
Outline the equation for calculating relative atomic mass
From relative abundance
(Sum of) isotopic mass x relative abundance
All over total relative abundance
How do diatomic molecules effect mass spectrometry
Cl and Br have two isotopes
The two isotope masses add together to create a combined mass
Creating three peaks for two isotopes
Eg Cl35 + Cl35, Cl35 + Cl37, Cl37 + Cl37
What causes the different relative atomic mass on other planets
Different abundance of isotopes
Different variants of isotopes
How can electron impact ionisation effect the appearance of the mass spectrum for a larger ion
Fragmentation occurs
Creating several peaks
The largest m/z is the full molecule
Called the parent ion or molecular ion
How does measuring the Mr with electro spray ionisation differ
Remove one for the mass of the H+ ion
What are the su levels in the 4th principle level
4s, 4p, 4d, 4f
How many electrons can each sub level hold
S - 2 pairs
P - 3 pairs
D - 5 pairs
F - 7 pairs
What does an orbital represent
The mathematical probability
of finding an electron at any point
within a certain spatial distribution around the nucleus
How does 4s act compared to 3d
4s gas less energy than 3D
So 4s is filled first
4s is further from the nucleus than 3d
So 4s is lost first
Outline chromium a electronic structure
1s2 2s2 2p6 3s2 3p6 4s1 3d5
Outline coppers electronic structure
1s2 2s2 2p6 3s2 3p6 4s1 3d10
Why do chromium and copper have different electronic structures
To minimise repulsion
4s2 pair has more repulsion
Than 3d5/3d10
Define first ionisation energy
The enthalpy change
when one mole of gaseous atoms
forms one mole of gaseous ions
with a single positive charge
Define second ionisation energy
The enthalpy change
When one mole of gaseous ions
With a single positive charge
Forms one mole of gaseous ions
With a double positive charge
First ionisation equation
H(g) > H+(g) + e-
Ti+(g) > Ti2+(g) + e-
What are the factors affecting ionisation energy
Proton number
Atomic radius
Shielding
Outline how proton number effects ionisation energy
More protons
Greater attraction of e- to nucleus
E- harder to lose
Outline how atomic radius effects ionisation energy
Bigger atom
Electron further from the nucleus
Less attraction
Electron easier lost
Outline how shielding effects ionisation energy
More shielding
Electron more repelled
Electron further from nucleus
Electron easier lost
Why are successive ionisation energies always larger
Second ionisation is bigger than first
Positive ion is formed in first ionisation
Ion increases attraction to the nucleus
Increasing the energy required to remove more electrons
What causes large jumps between successive ionisation energies
a change in shell
The latter energy is higher
Because it is closer to the nucleus
As it is in a different energy she’ll
Define periodicity
A repeating pattern across a period
Outline the shape of first ionisation energy from H to Ne
Large jump from H to He
Larger drop from He to Li
Small jump from Li to Be
Slight drop from Be to B
Increase from B to N
Slight drop from N to O
Increased from O to Ne
Outline the shape of first ionisation energy from Ne to Ar
Large drop from Ne to Na
Small jump from Na to Mg
Small drop from Mg to ask
Increase from Al to P
Slight drop from P to S
Increase from S to Ar
Outline why helium ahs the largest first ionisation energy
First electron is in first shell closest to nucleus
No shielding
More protons than H
Why do first ionisation energies decrease down the group
Outer electrons are further from the nucleus (larger radius)
More shielding
Attraction becomes smaller
Electron easier lost
Why is there a general increase in fest ionisation energy across a period
Electrons are added to the same shell across the period
Same radius size
Same shielding more protons
Larger attraction of e- to nucleus
Why is there a drop between Na and Ne
Na has outer electron in 3s shell
3s further from nucleus and more shielded
Has outer electron easier to remove
Why is there a drop between Mg and Al
Al filling 3p sub shell
Mg has outer electrons in 3s sub shell
3p are easier to remove
because they have higher energy
And are slightly shielded by 3s electrons
Why is there a small drop from P to S
S has 4 electrons in 3p sub shell
Creating a pair of electrons
This creates a slight repulsion
Making the electron easier to remove
