Atomic Structure Flashcards by Angel Ssemanda

What does a Mass Spectrometer measure?

The relative mass of isotopes

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What are the stages a Time of Flight mass spectrometer?

• ionisation
• acceleration
• ion drift (distance)
• detection
• analysis

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Outline Electrospray Ionisation

sample dissolved in polar solvent
injected through a needle at a high voltage
each particle gains a proton (H+) to form 1+ ions

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What is the equation for electrospray?

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

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What is electron impact?

• high energy electrons fired from electron gun
• knocks of an electron from each particle
• form 1+ ion

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What is the equation for Electron impact?

X(g) > X(g) + e-

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What happenes during Acceleration in TOF?

• positive ions are accelerated by an electric field to a constant KE
( velocity depends in mass of ion)
Ions with lower mass travel faster

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What happens during Ion Drift in TOF?

• ions separate
• they drift in a flight tube of know distance and time taken is recorded
• TOF depends on velocity

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What happens during ion detection in TOF?

• positive ions hot detector and pick up an electron
• causes a current to flow
( more ions hitting detector bigger current)

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Why is a vaccum required in TOF

So no other particles can be detected and interfere

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Equation for mass(kg) of each 1+ particle

( Mass number/Avagadro ) / 1000

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Equation to find Velocity with KE and mass

v = √2KE / m

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What equation can you use if you’re not given distance?

m1 m2
—- = —-
(t1)2 (t2)2

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What is the formula for relative atomic mass

average mass of an atom of an element
——————————————————-
1/12 mass if an atom an atom of 12C

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Equation to calculate relative atomic mass from peaks

sum (m/z of a peak x abundance of that peak)
————————————————————
sum of abundances

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what is fragmentation?

Bonds in covalent bonds break into fragments during electron impact ionisation

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What happens during fragmentation

bonds will gain a postitive charge
these give a peak

What fragmentation happens in Electrospray

little fragmentation occurs so there are less peaks

What is the Mr in Electrospray ionisation

the highest peak value minus one

What is the Mr in Electron impact?

The peak with the highest m/z value

What are shells matching sub-levels??

1 = s
2 = p
3 = d
4 = f

What is the order of increasing energy levels?

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s….etc

What are the maximum number of electrons in each sublevel

s = 2
p = 6
d = 10
f = 14

Why does 4s fill before 3d

4d is lower in energy

Why does Cr and Cu differ in electron configuration?

instead of 4s2 they have 4s1 they **show a full/half subshell** they have **lower energies and represent more stable arrangements**

What is first ionisation energy?

The minimum amount of energy required to remove an electron from a gaseous atom

What is the trend of Ionisation energy down a group and why?

• decreases • bc it’s removed from a HIGHER principle energy level • electron further from • more sheilding • less energy required to remove electron

What is the trend of Ionisation energy across a group and why?

• increases • protons increase • constant sheilding • more energy needed to remove electrons

What is the mass of a proton

What is the mass of a neutron?

what is the mass of an electron

1/1800

what is an isotope

atoms of an element with the same number of protons but different number of neutrons

what is the definition of mass numbers

total number of protons and neutrons

define atomic number

number of protons in an atom

define atomic number

number of protons in an atom

What is the equation for the first ionisation of an element?

X(g) > X+(g) + e-

What is the equation for the second ionisation of an element?

X+(g) > X2+(g) + e-

Describe successive ionisation energies

will always increase: - +ve charge on ion increases and ionic radius decreases - shielding is constant and nuclear attraction to outer electron is stronger