Atomic Structure

Question 1

Name the 3 subatomic particles

Answer 1

Proton, neutron, electron

Question 2

What is the relative mass of an electron

Answer 2

1/2000 or 1/1840

Question 3

What letters do we use to represent mass number and atomic number

Answer 3

Mass number = M and Atomic number = Z

Question 4

How is a positive ion formed

Answer 4

By losing electrons

Question 5

What ion would be expected to be formed by an element in group 6

Answer 5

2- ion

Question 6

What is the formula of the sulfate ion

Answer 6

SO42-

Question 7

Write the chemical formula of calcium nitrate

Answer 7

Ca(NO3)2

Question 8

Define isotope

Answer 8

Isotopes are atoms of the same element (same number of protons) with different numbers of neutrons

Question 9

Calculate the number of neutrons in C12 and C14

Answer 9

6 in C12 and 8 in C14

Question 10

Why do isotopes have the same chemical properties

Answer 10

Same number of electrons

Question 11

Describe the atomic model proposed by JJ Thompson

Answer 11

Plum pudding model, sphere of positive charge with electrons dotted around

Question 12

Describe the experiment of Rutherford where he discovered the nucleus

Answer 12

Fired alpha particles at gold foil and some deflected and a few bounced back showing small centers of positive charge

Question 13

Describe the atomic model proposed by Bohr

Answer 13

Positive nucleus surrounded by electrons in defined shells

Question 14

How could you calculate the mass of one atom of oxygen using its Ar of 16

Answer 14

16 divided by the Avagadro’s constant (6.022 x 10^23)

Question 15

What is meant by relative atomic mass

Answer 15

Mean mass of atoms of an element relative to the mass of 12g of carbon 12

Question 16

What are the 5 main stages in mass spectrometer

Answer 16

Vaporisation, Ionisation, acceleration, drift, detection

Question 17

Write generic equations to show the ionisation of X in a mass spectrometer by electron impact and proton absorbtion.

Answer 17

e- +X (g) –> X+ (g) + 2e-

X + H+ ——> XH+

Question 18

Write a generic equation to show the ionisation of X in a TOF mass spectrometer

Answer 18

H+ +X (g) –> XH+ (g)

Question 19

What are the two methods of ionisation that could be used in a mass spectrometer?

Answer 19

electron impact and electrospray

Question 20

Describe what happens during electrospray ionisation

Answer 20

Particles gain a proton

Question 21

Compare the speed and kinetic energy of a lithium and potassium atom in TOF mass spectrometry

Answer 21

Speed of lithium faster than potassium. Both have same KE

Question 22

What is meant by the molecular ion peak

Answer 22

The highest m/z value on the spectrum of a molecule, formed when the molecule does not break up

Question 23

How do you work the RMM in a TOF mass How do you work the RMM in a TOF mass spectometer

Answer 23

Subtract one from the mass of the molecular ion

Question 24

Why is m/z used in a mass spectrum not just mass

Answer 24

Because atoms can be doubly ionised and would be accelerated more quickly

Question 25

How are ions detected in a mass spectrometer?

Answer 25

ions hit the detector and gain electrons, which causes a current to flow

Question 26

How can you determine the number of ions hitting the detector at a m/z value?

Answer 26

The size of the current indicates how many ions of that m/z ratio are hitting the detector

Question 27

Calculate the Ar of an element sample which is made up of 75% C12 and 25% C14

Answer 27

12.5

Question 28

How many electrons can the s, p and d subshells each hold

Answer 28

s = 2, p = 6, d = 10

Question 29

Write the electronic configuration of an element with 20 electrons

Answer 29

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

Question 30

Write the electronic configuration of an elements with 24 electrons

Answer 30

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

Question 31

Which two transition metal elements do not have a full 4s orbital

Answer 31

Chromium and copper

Question 32

As a general rule which energy levels do electrons fill first?

Answer 32

Electrons fill orbitals in order from lowest energy to highest energy

Question 33

Which subshell fills first 4s or 3d?

Answer 33

4s

Question 34

From which subshell are electrons removed first during ionisation 4s or 3d?

Answer 34

4s

Question 35

Into what orbitals would two electrons in a p subshell go?

Answer 35

Electrons fill orbitals singularly before pairing up

Question 36

Fe has electron configuration [Ar] 4s2 3d6. what is the electron configuration of the Fe3+ ion

Answer 36

[Ar] 3d5

Question 37

Define first ionisation energy

Answer 37

The energy required to remove one mole of electrons from one mole of atoms in the gaseous state

Question 38

Write an equation to show the 1st ionisation energy of sodium

Answer 38

Na(g) ------> Na+(g) + e-

Question 39

Write an equation to show the 4th ionisation energy of calcium

Answer 39

Ca3+(g) ------> Ca4+(g) + e-

Question 40

Is ionisation energy exothermic or endothermic

Answer 40

Endothermic - requires energy

Question 41

How does nuclear charge affect ionisation energy

Answer 41

Increasing nuclear charge increase ionisation energy as electrons harder to remove

Question 42

How does 1st ionisation energy change down the group and give 2 reasons why

Answer 42

Decreases down group. Electrons further from nucleus so less attraction and more shielding so less attraction

Question 43

Write an equation to show the third ionisation energy of nitrogen

Answer 43

N2+ --> N3+ + e-

Question 44

Why do group 3 elements eg. Al, not fit the trend in increasing first ionisation energy across the period

Answer 44

Electrons removed from a p orbital which is further from the nucleus so less attraction so ionisation energy decreases

Question 45

Why do group 6 elements eg. O, not fit the trend in increasing first ionisation energy across the period

Answer 45

Electrons removed from an orbital which contains two electrons which gives some repulsion so easier to remove. So ionisation energy decreases