Atomic Structure - Chapter 1 Flashcards
What is an atom
It is the smallest part of an element that can exist and still retain all the features of that element
What particles make up atoms
Protons
Neutrons
Electrons
Relative mass of Protons, Electrons and Neutrons
1
1
1/1800
What holds together protons and neutrons
The strong nuclear force
what holds the electrons in the energy levels
electrostatic attraction
What is the Mass number
Total number of protons and neutrons
What is the atomic number
Number of protons
What are Isotopes
They are atoms of the same element with the same atomic number but different mass numbers
What is relative atomic mass
It is the average mass of an atom of an element on a scale where an atom of carbon 12 is exactly 12
what can a mass spectrometer be used to find out about
Relative atomic mass
Relative molecular mass
Relative abundances of iostopes
what 4 things happen in a TOF mass spectrometer
ionisation
Acceleration
Ion drift
Detection
What happens in ionisation
The sample is ionised by 2 different techniques
Electron impact
Electrospray ionisation
What is electron impact
The sample is vaporised and high energy electrons are fired at it
The electrons come from an electron gun, which is a hit filament with a current running through it
What does electron impact cause
It knocks off one electron from each particle
Sometimes causes fragmentation
What is Electrospray Ionisation
The sample is dissolved in a polar solvent which can act as a source of protons
The solution is pumped through a capillary needle at a high voltage
This causes an aerosol to form and evaporates and the molecule to gain a H+
What does Electrospray Ionisation cause
An H+ ion to attach
Doesn’t cause fragmentation
What is acceleration
It is the acceleration of the positively charged ions by applying an electrical field to a series of plates
The electric field gives the same kinetic energy to all the ions
The Ions with a lower m/z ratio will accelerate more
What is the potential energy equation
PE = q x V
charge on particle x voltage
What is the kinetic energy equation
KE= 1/2mv2
What is ion drift
All ions leave the electric field with a constant speed ad kinetic energy
The lighter ions will travel to the detector quicker than those with a higher m/z
Equation for velocity
v= d/t
Equation for the kinetic equation and the velocity equation combined
KE= 1/2 m (d/t)2
What links the TOF and m/z ratio
The time of flight is proportional to the mass to charge ratio
What is detection
The detector detects the current created when the ions hit it and gain electrons
It records how long they took to pass through the instrument as well as the abundance of each ion
How many electrons can fit into energy levels 1 - 4
2
8
18
32
What are orbitals
they are sub levels within each energy level
They are a volume of space around a nucleus in which there is a high probability of finding an electron
Each hold a maximum of 2 electrons
What are the different types of orbitals
s
p
d
f
How many sub orbital pairs are in each type of orbital
s -1
p-3
d-5
f-7
what is different about the orbital 4s
It has a lower energy than 3d and so is filled up before 3d
What is Aufbau principle
An electron will always fill the available orbital of the lowest energy
What is Pauli exclusion principle
Each orbital can hold a maximum of 2 eletrons
What is Hund’s rule
Atomic orbitals of the same energy will fill singly with electrons of the same spin before pairing of electrons occurs
What is ionisation energy
It is the energy required to remove 1 mole of electrons from 1 mole of an element in its gaseous state
How can IE data show which group an element is in
It can be seen as the massive jump in IE
Why does ionisation energy decrease as you down the group
The nuclear charge increases as you go down the group
Outermost electrons are in energy levels that are increasingly further away from nucleus
Inner electrons shield outer electrons and allow them to be removed easier
What happens to ionisation energy as you go along the period
It increases
Nuclear charge increases
Atomic radius is similar
More shielding
Why is 1st IE for aluminium less than Mg’s
Although Al has a higher nuclear charge than Mg, its outermost electron is in a 3p orbital which is further from the nucleus than 3s orbital so less energy required
Why is there a slight drop in 1st IE between phosphorus and sulphur
In P orbital, each of the 3 electrons occupies a different 3p orbital whilst in sulphur one iof the 3p orbitals must contain 2 electrons. The repulsion between the electrons makes it easier to remove one
Why are the ions charged in TOF mass spectrometer
So the ions will interact and be accelerated by the electric field
Ions create a current when hitting the detector so they can be detected
