Atomic Structure

Question 1

How has the atomic structure changed over time?

Answer 1

Neils Bohr- idea of tiny positive nucleus orbited by electrons in shells
Schrödinger- idea of electrons as waves and particles (quantum theory)
Chadwick- discovered neutron

Electrons used to be seen as solid particles but now they are viewed more as a negatively charged cloud

Question 2

What is the charge and mass of a proton, neutron and electron?

Answer 2

Proton mass- 1
Proton charge- +1

Neutron mass- 1
Neutron charge- 0

Electron mass- 1/2000
Electron charge- -1

Question 3

Describe the structure of an atom

Answer 3

An atom consists of a nucleus containing positive protons and neutral neutrons. The positive nucleus is surrounded by negatively charged orbiting electrons

Question 4

Define the following:
Mass number (A)
Atomic number (Z)

Answer 4

Mass number is the total number of protons + neutrons
Atomic number is the number of protons

Question 5

What is an isotope and how to same element isotopes react?

Answer 5

Isotopes are atoms with the same number of protons but different number of neutrons
Same element isotopes react chemically in exactly the same way due to them all having the same number of electrons

Question 6

What is mass spectrometry used for?

Answer 6

A mass spectrometer gives accurate information about relative isotopic mass and relative isotope abundances

Question 7

What are the names of the two types of ionisation?

Answer 7

Electro spray
Electron impact

Question 8

How does electrospray ionisation work?

Question 9

How does electron-bombardment work?

Question 10

What are the chambers of the mass spectrometer?

Answer 10

Ionisation
Acceleration
Ion drift
Ion detection
Data analysis

Question 11

What happens in the ionisation chamber?

Answer 11

Gaseous atoms turn into gaseous ions

Question 12

What happens in the acceleration chamber?

Answer 12

Positive ions are attracted to the negatively charged plate
All the ions have the same kinetic energy
Light ions travel faster
Heavier ions travel slower

Question 13

What happens ion drift?

Answer 13

Ions travel through a hole forming a beam and continue travelling along the flight tube

Question 14

What happens in ion detection?

Answer 14

Positive ions pick up an electron forming a current which is then recorded
Light ions reach the detection plate first

Question 15

What happens in data analysis at the end of mass spectrometry?

Answer 15

Signals from the detectors are passed on to the computer which produces mass spec diagrams that we then can use to calculate isotopic abundances

Question 16

What is the formula used to calculate Ar of an isotope?

Question 17

What is an electron?

Answer 17

A cloud of negative charge

Question 18

What are the first 3 sub shells and how many orbitals does each sub shell have?
How many electrons can each orbital hold?

Answer 18

S- 1 orbital and holds 2 electrons
P- 3 orbitals and holds 6 electrons
D- 5 orbitals and holds 10 electrons

4s orbital is filled before 3D due to having a lower energy level

Question 19

What are the 2 elements that have exceptions when writing their electronic configurations and wrote their configuration.

Answer 19

Exception= chromium and copper

Cr (24 e-) — 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Rather than being [Ar] 4s2 3d4 it is [Ar] 4s1 3d5 because the d orbital is more stable when it is either half full or completely full

Cu (29 e-) — 1s2 2s2 2p6 3s2 3p6 4s1 3d10
Rather than being [Ar] 4s2 3d9 it is [Ar] 4s1 3d10 because the d orbital is more stable when it is either half full or completely full

Question 20

Define first ionisation energies

Answer 20

Energy required to remove one mole of an electron from one mole of gaseous atoms

X (g) —> X+ (g) + e-

Question 21

What are successive ionisation energies and write equations to show this

Answer 21

Successive ionisation energies mean second… third… fourth and so on

First= X(g) —> X+(g) + e-
Second= X+(g) —> X2+ (g) + e-
Third= X2+ (g) —> X3+ (g) + e-

The amount of energy needed to remove successive electrons increases as the electrons get closer to the nucleus so they have a stronger attraction

Question 22

What is the trend in first ionisation energy in period 3?
(Include any deviations)

Answer 22

Ionisation energy increases across period 3
Deviations= Al and S
Aluminium has electrons in 3p which is higher energy level so require less energy to be removed
Sulphur has a paired electron so there’s greater repulsion so less energy is needed to remove electrons

Question 23

What is the trend in first ionisation energy down group 2?
(Include any deviations)

Answer 23

Ionisation energy decreases down group 2
Although nuclear charge increases the distance between outer shell electrons and nucleus also increases, therefore there’s less attraction and thus less energy required to remove the electrons