Atomic Structure

Question 1

4 stages of mass spectrometry

Answer 1

Electrospray ionisation
Acceleration
Ion drift
Detection

Question 2

Describe the electrospray ionisation process in mass spectrometry

Answer 2

The sample is dissolved in a polar solvent and pushed through a small nozzle at a high pressure. A high voltages is applied to the sample, causing the particles to lose an electron and become positively charged. The ionised particles are separated from the solvent, leaving a gas made up of positive ions

Question 3

Describe the acceleration process that occurs in mass spectrometry

Answer 3

The positive ions are accelerated by an electric field. The electrics field gives the same kinetic energy to all the ions

Question 4

Why must the particles in the acceleration stage of mass spectrometry be positive?

Answer 4

They need to be positively charged in order to be accelerated by the electric field

Question 5

What happens to ions with a lower mass/charge ratio in the acceleration stage of mass spectrometry?

Answer 5

They experience a greater acceleration because of the fact that they receive as much energy as heavier ions

Question 6

Describe the ion drift process of mass spectrometry

Answer 6

The ions leave the electric field with a constant speed and constant kinetic energy. They enter a region with no electric field and drift through it at the same speed as they left the electric field

Question 7

Describe the detection process of mass spectrometry

Answer 7

When the ions hit the detector, a current is created and the detector records how long they took to pass through the spectrometer. This data is then used to calculate the mass/charge values needed to produce a mass spectrum

Question 8

Calculating relative atomic mass from a mass spectrum

Answer 8

Multiply the relative isotopic abundance by the relative atom mass
Add the totals
Divide answer by the total relative abundance (100 if % was used)

Question 9

electron configuration order

Answer 9

1s (x2)
2s (x2)
2p (x6)
3s (x2)
3p (x6)
4s (x2)
3d (x10)
4p (x6)
5s (x2)
4f (x14)

Question 10

Why does the 4s sub shell fill up before the 3d sub shell?

Answer 10

It has a lower energy level, despite the fact that its principle quantum number is bigger

Question 11

Explain noble gas shorthand notation

Answer 11

Put the noble gas before the element in square brackets then write out the remaining electrons using electron configuration

Question 12

Give the electron configuration of silicon

atomic number - 14

Answer 12

1s2, 2s2, 2p6, 3s2, 3s2

Question 13

Give the electron configuration of potassium

atomic number - 19

Answer 13

1s2, 2s2, 2p6, 3s2, 3p6, 4s1

Question 14

Give the noble gas shorthand notation of calcium

atomic number - 20

Answer 14

[Ar] 4s2

Question 15

Give the noble gas shorthand notation of iodine

atomic number - 53

Answer 15

[Kr] 5s2, 4d10, 5p5

Question 16

Give the electron configuration of chromium

atomic number - 24

Answer 16

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5

Question 17

Give the electron configuration of copper

atomic number - 29

Answer 17

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10

Question 18

Why are the electron configurations of copper and chromium different from what is expected?

Answer 18

They each donate 1 electron from the 4s sub shell to the 3d sub shell because it makes them more stable

Question 19

Which groups are in the s block of the periodic table?

Answer 19

Groups 1 and 2

Question 20

What bonds are formed by the s block elements and why?

Answer 20

Ionic bonds because the atoms are in groups 1 and 2 so easily lose their outer electrons (which are found in the s sub shell)

Question 21

What 3 things affect ionisation energy?

Answer 21

Nuclear charge
Distance from nucleus
Shielding

Question 22

How does nuclear charge affect ionisation energy?

Answer 22

The more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons

Question 23

How does nuclear distance affect ionisation energy?

Answer 23

Attractions falls off very rapidly with distance. An electron close to the nucleus will be much more strongly attracted than one further away

Question 24

How does shielding affect ionisation energy?

Answer 24

As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction to the nucleus. This lessening of the pull of the nucleus thanks to the inner electron shells is called shielding

Question 25

General equation for ionisation energies

Answer 25

X(n-1)+ —> Xn+ + e-

Question 26

Describe the ionisation energy trend down group 2

Answer 26

The first ionisation energy down group 2 decreases

Question 27

Explain the ionisation energy trend down group 2

Answer 27

As you go down group 2, the ionisation energy decreases. This is because shielding increases so the attraction between the positive nucleus and outer negative electron decreases; so the outer electron is lost easier. Due the increased shielding, the distance between the outer electron and the nucleus also increases. This also decreases the attraction forces between the nucleus and outer electron so it is lost easier

Question 28

Describe the general trend of ionisation energies

Answer 28

Across a period, the general trend of ionisation energies increases

Question 29

Explain the general trend of ionisation energies across a period

Answer 29

Across the period, the number of protons increase. This increases the nuclear charge which increases the attraction forces between the positive nucleus and negative outer electron; so it is harder to lose the outer electron

Question 30

Explain the drop in ionisation energies between magnesium and aluminium, across period 3

Answer 30

Aluminium has a lower ionisation energy that magnesium. This is because the outer electron of aluminium is in the 3p orbital whereas the outer electron of magnesium is in the 3s orbital. The 3p orbital is further away from the nucleus than the 3s orbital. This means the attraction forces between aluminium’s outermost electron is weaker than that of magnesium’s so it is lost more easily. Shielding is also increased by the fact that aluminium’s outer electron is in the 3p orbital. This too lowers the attraction forces between the nucleus and the outer electron, making it easier to lose.

Question 31

How does repulsion affect the first ionisation energy?

Answer 31

Two electrons in the same orbital repel one another. This offsets the attraction of the nucleus, causing the electrons to be lost more easily

Question 32

Explain the drop in ionisation energies between phosphorus and sulfur, across period 3

Answer 32

Sulfur has a lower first ionisation energy than phosphorus. This is because the electron being removed from sulfur occupies an orbital containing two electrons. These electrons repel one another which offsets the attraction of the nucleus and makes it easier to lose the electrons. The electron being removed from phosphorus is in a single occupied orbital so doesn’t experience this repulsion

Question 33

What is Avogadros constant?

Answer 33

6.02x10^23

Question 34

Number of particles

Answer 34

Number of moles x avogadros constant

Question 35

Ideal gas equation

Answer 35

pV=nRT

Question 36

Units of all parts of ideal has equation

Answer 36

P = Pa
V = m3
R = JK-1mol-1
T = K
n = miles

Question 37

The value of gas constant

Answer 37

8.31 JK-1mol-1

Question 38

1 dm3 to m3

Answer 38

1x10-3

Question 39

1 cm3 to m3

Answer 39

1x10-6