Topic 1 Atomic Structure & Periodic Table

Question 1

What is a mass number?

Answer 1

number of protons and neutrons in the nucleus of an atom

Question 2

What is a relative isotopic mass? (2 marks)

Answer 2

the mass of an atom of the isotope compared to 1/12th of Carbon-12 (1)
which has mass of 12

Question 3

What is a relative atomic mass? (Ar)

Answer 3

the weighted mean mass of all isotopes of an element relative to 1/12 of the mass of an atom of carbon-12

Question 4

What is a Relative Molecular Mass? (Mr)

Answer 4

Aka relative Formula mass (esp when it is an ionic compound)

the sum of Ar present in a molecule

Question 5

What is an orbital?

Answer 5

A region within an atom that can hold up to two electrons with opposite spins.

Question 6

Define isotopes (2 marks)

Answer 6

The element with same number of protons but different numbers of neutrons

Question 7

Definition of first IE (2 marks)

Answer 7

energy needed to remove 1 mole of electrons from a gaseous atom
X (g) -> X+ (g) + e-

Question 8

Definition of second IE

Answer 8

Energy required to remove 1 mole of electrons from 1 mole of 1+ gaseous ions to form 1 mole of 2+ gaseous ions under standard conditions

Question 9

What is a successive IE

Answer 9

the energy that is required to remove the electron one after the other

Question 10

3 factors affecting IE

Answer 10

• nuclear charge (num of protons)
• attraction
• shielding
  (- atomic radius that decreases down a period)

Question 11

What is periodicity?

Answer 11

Pattern/trend of physical/chemical properties repeated across a period

Question 12

What are the 6 stages off mass spectrometry?

Answer 12

Vapourisation
Ionisation
Acceleration
Deflection
Detection (1+ charge as E- knocked off)

Question 13

The bigger the ion… (in terms of mass spectrometry)

Answer 13

The less the deflection

Question 14

Only what are detected in mass spectrometry?

Answer 14

Ions (1+ charge)

Question 15

Why is mass spectrometry taken place in a vacuum?

Answer 15

So don’t slow molecules down from deflections
And prevent collisions with air particles

Question 16

What does mass spectrometry tell you?

Answer 16

• fragments of ions in a molecules

Question 17

What does infrared tell you?

Answer 17

• functional groups
• dnf

Question 18

Define periodicity
In terms of atomic radii of period 2 and 3 elements.

Answer 18

It is the repeated physical and chemical properties across a period (with increasing atomic number)
Atom radii decreases from left to right due to increased attraction between nucleus and e-s
Also repeated in Period 3

Question 19

what are isotopes?

Answer 19

atoms of the same element with same num of protons but diff num of neutrons

Question 20

State and explain the trend in first IE down periodic table groups (except G3). 2 marks

Answer 20

Decreases down
- increasing number and energy of subshells
- increasing atomic radius and sheilding
- so lose outer e easier

Question 21

why is first IE of Boron less than Beryllium, even though Boron has higher nuclear charge?

Answer 21

Be - 1s2 2s2
B - 1s2 2s2 2p1
B’s outer e has higher energy in a higher energy orbital
but there is more electron-electron repulsion in the 2s2 orbital (Be) as opposed to 1 in 2p1 (B)

Question 22

what is periodicity?

Answer 22

repeating patterns across a period of the periodic table

Question 23

what is the first IE trend across Period 3? (3 marks)

Answer 23

• due to increasing nuclear charge
• e-s added to the same quantum shells so increase of shielding is minimal
• energy of outer e-s decrease (outweighed by increasing nuclear charge)
  [i dont rlly like this Q]

Question 24

what is the trend in atomic radii across period 3? (3 marks)

Answer 24

decreasing atomic radii
since nuclear charge is increasing
increasing attractive force of electron-electron repulsion, num of outer quantum shell increases

Question 25

what species of chlorine is responsible for each peak at m/z 70, 72, 74?

Answer 25

35Cl-35Cl+ makes 70
35Cl-37Cl+ makes 72
37Cl-37Cl+ makes 74
dont forget the + sign!!

Question 26

why is the first IE of sodium lower than magnesium?

Answer 26

sodium has lower nuclear charge
so orbital energy of outer electron in 3s is lower
(always write out electron configuration when asked to compare ie)

Question 27

more electron-electron repulsion =

Answer 27

greater shielding

Question 28

Which 2 elements have special electronic configurations?

Answer 28

Chronium (Cr-24) and copper (Cu-29)

Question 29

What is the electronic configuration of chronium? (Ar=24)

Answer 29

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

Question 30

What is the electronic configuration of copper? (Ar=29)

Answer 30

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

Question 31

Why do isotopes of the same element have the same reactivity?

Answer 31

they have the same electronic config (so same num of e-s)

Question 32

How are ions deflected in mass spectrometry?

Answer 32

Magnetic field

Question 33

Why is sodium sulfide’s mp higher than sodium chlorides?

Answer 33

Higher charge (2-) in sulfides than chlorides (1-)
Attractive force between sodium is higher

Question 34

In terms of fundamental particles, why are isotopes 10-B and 11-Boron have similar chemical reactions?

Answer 34

Both have 5 electrons, identical electronic configurations

Question 35

Explain why the second ionisation energy of boron is higher than first I.e. (1 mark)

Answer 35

Removing an electron from a +ve ion will need more energy

Question 36

What is the effect of electron repulsion from opposite spin in orbitals?

Answer 36

When the highest energy electron is in an orbital with another electron, they repel each other, push each other further from the nucleus
Decreases the electrostatic forces of attraction
So less energy needed to ionise

Question 37

How is an ion deflected?

Answer 37

With a magnetic field

Question 38

Br has isotopes 79Br and 81Br. Why is there a small peak at 80Br? (2 marks)

Answer 38

Br2 has mass of 158 and 162
Br2 2+ has m/z of 80