3.1.1.2 MASS NUMBER AND ISOTOPES TOF + questionsss

How is atomic number presented

Z and is equal to number of protons

WHAT DOES MASS SPECTROMETRY DO?

Gives accurate information about relative isotopic mass + relative abundance of isotopes

What is the relative atomic mass?

The mean mass of an atom of an element divided by one twelfth of the mean mass of an atom of the carbon-12 isotope

What is meant by an isotope

Atoms of the same element

Same. Atomic number

Different number of neutrons

Therefore different mass number

What is meant by an ion?

When an atom loses or gains electrons

No overall charge

No longer neutral

An ion with one fewer proton one fewer neutron and the same number of electrons as an atom of 129xe

A particle with 2 fewer protons two fewer neutrons and the same number of electrons as an atom of 20ne

An ion with one more proton two more neutrons but the same number of electrons as an ion of 85RB+

What does abundance mean?

How common each isotope is

What is mass spectrometry used for?

Molecular/ atomic Mass number

abundance of isotopes

What is TOF and what is it used for

Time of flight mass spectrometry

Differentiates molecules based on time taken for them to travel through the machine

What are all the stages called to T.OF

First it’s vapouriest to become a gas then placed into the spectrometer where its ionised

Ionisation

Acceleration

Ion drift

Detection

Describe the different types of ionisation

ELECTRON BEAM IONISATION - electron gun used to fire HIGH ENERGY ELECTRONS at sample

Electrons repel each other + TAKE ONE ELECTRON OFF ATOM OR MOLECULE + 1+ ion

(Used for low MR components and elements)

Electro spray IONISATION

SAMPLE IS DISSOLVED INTO A VOLATILE SOLVENT

Injected through a HYPER DERMIC NEEDLE turns sample into a mist at end of needle - HAS A HIGH VOLTAGE - CAUSES PARTICLES TO GAIN A PROTON = ION

X(g) + H(g)^+ >. XH(g)

Used for hgh Mr compounds EG PROTEIN

Describe acceleration

Accelerated by an electric field ( due to them being charged)

Negative on front (acceleration plate) to attract ions and positively charged at back (to repel further down)

AFTER THIS ALL PARTICLES HAVE SAME INETIC ENERGY

Would a heavier mass or lighter mass be have a higher velocity

LIGHTER MASS ISOTOPES OR MOELCULES WILL HAVE HIGHER VELOCITY

What happens in ion drift?

Positive ions endete Right tube

How are ions then detected in DETECTIONSTAGE

Negatively charged plate which makes a current produced when ions hit the place

MORE IONS= BIGGER CURRENT

Mass of ions hitting the detection plate can be picked up and forms the time of flight

What has to happen for detection to work?

PARTCILES MUST BE CHARGED

So that they can be attracted to negative and positive plates and move down the spectrogram

What is the layout of the mass spectrum

What is normally the charge?

+1

So in electron BEAM the peak equals the relative mass of isotope

ELECTRON SPRAY. - the peak is one unit greater than relative mass ( cux of the H+ ION so make sure to minus one) -..

How to get mass of an element to be used in the kinetic energy equation

How to get the time of flight equation? FROM KINETIC EQUATION AND SPEED DISTANCE TIME

HOW TO GET RELATIVE ATOMIC MASS

What does species mean?

Specific type of atom or ion in the molecular compound

What does m+ mean

Positive ion when electron is knocked of in ionisation

The m is the parent element

What is hydrogen 2 called

Deuterium

It has one proton and one neutron

An isotope of hydrogen

Explain what a small peak can be( m+1)

It’s one added to mass number

Explain what m+2 can be?

:.

Why is m+1 peaks higher than m+2 peaks

Abundance of it is higher ( likelihood of an m+1 is more)

Questionnn

The element bromine is made of diatomic molecules. THERE are 2 isotopes of bromine namely 79br and 81br of roughly equal abundance. Sketch what the time of flight mass spectrum of the element bromine will look like?

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