1.1-1.5 Physical chemistry

Question 1

How is the relative mass of an electron different from proton and neutron?

Answer 1

Its value it 1/1836 whereas theres is 1

Question 2

Define an isotope

Answer 2

An element with the same amount of protons and electrons but different number of netrons

Question 3

Why do isotopes of the same element display the same characteristics?

Answer 3

They still have the same number of electrons in their outer shell

Question 4

Define relative isotopic mass

Answer 4

Mass of an isotope relative to a 1/12th of carbon 12 atom

Question 5

Define relative atomic mass

Answer 5

The average mass of an atom relative to a 1/12th of a carbon-12 atom

Question 6

How do you calculate relative atomic mass from mass spectra?

Answer 6

(Relative abundance x mass) + (relative abundance x mass) etc all over 100

Question 7

Define ionisation energy

Answer 7

The amount of energy required to move one mole of electrons from one mole of gaseous atoms of an elememt to form one mole of gaseous ions.

Question 8

Define First ionisation energy

Answer 8

Energy required to remove one mole of electrons, from one mole of gaseous atoms of an element, to form one mole of gaseous 1+ ions.

Question 9

What are the units of ionisation energy?

Answer 9

Kilojoules per mole

Question 10

When does succesive ionisation energy occur?

Answer 10

Each time an electron (more than one) is removed from an atom there is succesive ionisation energy.

Question 11

Write an equation representing the second ionisation of an element.

Answer 11

X+(g) → X2+(g) + e-

Question 12

Why do succesive ionisation energies of an element increase?

Answer 12

Because once you have removed the outer electron from an atom, you have formed a positive ion.

Question 13

Why is removing an electron from a positive ion more difficult than from a neutral atom?

Answer 13

There is a greater electrostatic charge to the cation

Question 14

What happens to attractive forces in a positive ion as more electrons are removed and why?

Answer 14

It increases due to decreasing shielding and an increase in the proton to electron ratio

Question 15

What are the four factors that affect size of first ionisation energy?

Answer 15

-size of nuclear charge
-Distance of outer electrons from nucleus
-Shielding effect of inner electrons
-Spin pair repulsion

Question 16

What happens to ionisation energy across a period and why?

Answer 16

Increases
-Because, nuclear charge increases causing the atomic radius of atoms to decrease as outer shell is pulled closer to the nucleus and distance between nucleus and electrons decrease. Shielding remains constant. But it becomes harder to ove an electron meaning more energy is needed.

Question 17

When are atoms formed?

Answer 17

When an atom looses or gain electrons

Question 18

What is an m/z value?

Answer 18

Mass to charge ratio

Question 19

What are the five stages of mass spectrometry

Answer 19

Ionisation
Acceleration
Ion drift
Detection
Analysis

Question 20

What is the acronym to remember 5 stages of mass spectometry?

Answer 20

I am in detention always

Question 21

Describe what happens in the first stage of mass spectra?

Answer 21

This is the ionisation stage and a sample of an element is vapourised and injected into the mass spectrometer where high voltage is passed over the chamber. This causes electrons to be removed from the atoms (they become ionised) leaving charged ions in the chamber

Question 22

What happens in the second stage of mass spectra?

Answer 22

Positively charged ions are then accelerated towards a negatively charged detection plate.

Question 23

What happens in the third stage of the mass spectra?

Answer 23

The ions are the deflected by a magnetic field into a curved path. The radiation of their paths is dependent on the charge and mass of the ion.

Question 24

What happens in the fourth stage of the mass spectra?

Answer 24

Detection- this is where the positive ions hit the negatively charged detection plate and gain an elctron producing a flow of charge. The greater the abundance, the greater the current produced.

Question 25

What happens in the fith stage of mass spectra?

Answer 25

Values of the current are used in combination with flight times to produce a spectra print out with relative abundance of each isotope displayed.

Question 26

What does Ar mean?

Answer 26

Relative atomic mass

Question 27

What is the formula for calculating Ar from a mass spectra?

Answer 27

Total abundance

Question 28

Describe the trend in first ionisastion energy along a period

Answer 28

First ionisation energy increases due to a decreasing atomic radius and greater eletrostatic forces of attraction.

Question 29

Describe the trend in first ionisation energy down a group

Answer 29

It decreases down a group due to an increasing atomic radius and electron shielding which reduces the effect of electrostatic forces of attraction

Question 30

What does a sudden large increase indicate when an SIE graph is plotted and why does this occur?

Answer 30

This indicates a change in energy level, because, the elctron is being removed from an orbital closer to the nuclues so more energy is required to overcome the attraction.

Question 31

Explain why the first ionisation energy of aluminium would be lower than expected

Answer 31

This is due to single pair electrons with opposite spin, as a result, there is natural repulsion which reduces the amount of energy needed to be put in to remove the outer electron.

Question 32

What are the 4 types of orbiatls and how many can be held in them?

Answer 32

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

Question 33

Provide the three pieces of evidence for current model of electron configuration

Answer 33

Emission spectra
Succesive ionisation energy
First ionisation energy

Question 34

How is emission spectra evidence for electron configuration?

Answer 34

Each line in the emission spectrum corresponds to a specific amount of energy. This energy is emitted when electrons from higher-energy electron shells transition to a lower-energy shell. Different lines indicate that there are differences between in energy between shells. This is evidence that electrons are found in shells with discrete energy levels (quantum shells)

Question 35

Why do electrons pair up with opposite spin in an orbiatal?

Answer 35

So atom is as stable as posssible because they dont repel eachother

Question 36

Electrons in the same orbital must have….

Answer 36

opposite spins

Question 37

Give an exception to the ‘rules’ of drawing out electron configuration

Answer 37

If electron spins are unpaired and therefore unbalanced, it creates natural repulsion maming atom unstable, therefore electrons can take on different arrangment to prove stability.

Question 38

Give an exception to the ‘rules’ of drawing out electron configuration

Answer 38

If electron spins are unpaired and therefore unbalanced, it creates natural repulsion maming atom unstable, therefore electrons can take on different arrangment to prove stability.

Question 39

What happens to atomic radius along a period?

Answer 39

It decreases due to increased nuclear charge for the same number of electron shells. The outer electrons are pulled in closer to the nucleus as the increased charge produces a greater attraction. As a result, the atomic radius for that element is reduced.

Question 40

What happens to atomic radius down a group?

Answer 40

It increases because an electron shell is added each time you go down a group. Therefore this increases the distance between the outer shell electrons and the nucleus reducing the power of attraction. More shells aos increases electron shielding therefore nuclear attraction is reduced futher and aromic radius increases.

Question 41

What is electronegativity?

Answer 41

The ability of an atom to attract the pair of electrons in its covalent bond to itself

Question 42

When is a bond non-polar?

Answer 42

When two atoms in a covalent bond have the same electronegativity

Question 43

What is periodicity?

Answer 43

When elements across the period show repeating patterns in chemical and physical properties

Question 44

What is the trend in melting points across period 2 ?

Answer 44

Increases, peaks at silicon then decreases.

Question 45

Explain the melting point trend in period 2

Answer 45

Na, Mg and Al have metallic bonds and giant metallic structures whereas silicon has strong covalent bonds and a giant molecular structure then the elemts after that have simple molecular structures.

Question 46

Explain why there is a drop in ionsiation energy between groups 5 and 6?

Answer 46

The shielding is identical in for example phosphorus and sulfur atoms and the electron is being removed from an identical. In phosphorus’s case, the elctron is being removed from a single occupied orbital but in sulfur the electron is being removed from an orbital containing two electrons. The repulsion from the two electrons in a orbiatal means electrons are easier to remove from the orbital meaning it has a lower ionisation energy.

Question 47

What is the trend in atomic radius across a period?

Answer 47

it decreases as number of protons increase, strong eletrostatic charge of attraction between elecrons and protons increases making atomic radius smaller.

Question 48

What is the trend in ionsiation energy across a period?

Answer 48

Increases as it gets harder to remove outer electrons due to stronger nuclear attraction. There is little shielding effect.

Question 49

Why does aliminium drop in the trend of ionisation in period 3 elements?

Answer 49

it has a 3p orbital rather than 3s and 3p has slightly higher energy so electron is found futher from nucleus. 3p also adds additional shielding and both these things combined means result in drop in ionisation energy.

Question 50

Whta happens to the M.P and B.P of metals across a period and why?

Answer 50

Increases because metallic bonds get stronger as metal ions have increasing number of delocalised electrons so there is a stronger attraction between metal ions and delocalised electrons.

Question 51

What is the trend in M.P and B.P of giant covalent structures in a period?

Answer 51

Strong covalent bond linkins the atoms and a lot of energy needed to break bonds so they have the highest b.p and m.p in their period like carbon and silicon

Question 52

What are the boiling points of simple molecular structures like and why?

Answer 52

They are low depending on their london forces but they are weak and easy to overcome so they have low boiling and melting points

Question 53

identify some uses of mass spectra

Answer 53

-Mass spectrometers have been included in planetary space probes so that elements on other planets can be identified. Elements on other planets can have a different composition of isotopes.
-Drug testing in sport to identify chemicals in the blood and to identify breakdown products from drugs in body quality control in pharmaceutical industry and to identify molecules from sample with potential biological activity -Radioactive dating to determine age of fossils or human

Question 54

Potential errors in using a gas syringe

Answer 54

gas escapes before bung inserted •
syringe sticks •
some gases like carbon dioxide or sulphur dioxide are soluble in water so the true amount of gas is not measured.