ATOMIC STRUCTURE Flashcards by Kara-Leigh Addison

Lost the 3 sub atomic particles

Proton
Neutron
Electron

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What is the relative mass of an electron

1/1840

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Define atomic number

The number of protons in the nucleus

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Define mass number

The number of protons and neutrons in the atom

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Define isotope

Atoms with the same number of protons but different numbers of neutrons

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Outline the features of isotopes

Similar chemical properties
Due to same electronic structure

Slightly varying physical properties
Due to different masses

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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

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What are the 4 steps in a mass spectrometer

Ionisation
Acceleration
Flight tube
Detection

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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

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When is electron impact used?

Elements and substances with low formula mass

As larger organic molecules can fragment

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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

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When is electro spray ionisation used

Larger organic molecules

Softer conditions prevent fragmentation

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Outline acceleration in TofF mass spectrometry

Positive ions are accelerated

By an electric field

To a constant kinetic energy

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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

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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

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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

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What can a mass spectrometer measure

M/z (mass to charge ratio)

Abundance

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What happens if two electrons are removed

Halves the mass value

Due to m/z ratio

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Outline the equation for calculating relative atomic mass

from percentage abundance

(Sum of) isotopic mass x % abundance

all over 100(%)

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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