Atomic Structure

Question 1

What is an element?

Answer 1

A substance made up of only one type of atom

Question 2

What is a mixture?

Answer 2

A compound made up of two or more elements that are not chemically linked

Question 3

What is a compound

Answer 3

A substance made up of two or more chemical elements that are chemically combined

Question 4

What are atoms

Answer 4

The smallest part of a substance that cannot be broken down chemically

Question 5

What are molecules

Answer 5

Two or more atoms connected by chemical bonds

Question 6

Atomic number

Answer 6

(Z)
The number of protons in the nucleus of an atom of an element

Question 7

Mass number

Answer 7

(A)
Total number of protons and neutrons in the nucleus (nucleon number)

Question 8

Explain binding energy (BE)

Answer 8

The further the electron is from the nucleus, the less the BE
Outer electrons = weaker attractive forces
Inner electrons= stronger attractive forces
To overcome the forces of attraction of the nucleus and remove and electron

Question 9

Electron shells

Answer 9

K - 2
L - 8
M - 18

Question 10

What is valency

Answer 10

The ability of one atom to join another

Question 11

Ionic bonds

Answer 11

The transfer of electrons from one atom to another forming charged ion

Question 12

Covalent bonds

Answer 12

Sharing of electrons between atoms

Question 13

Pauli exclusion principle

Answer 13

No two electrons can be at the same state at the same time within the same matter

Question 14

What is a nuclide?

Answer 14

A particular variety of atom characterised by a given atomic number and a given mass (an element has a fixed Z and A)

Question 15

Isotopes

Answer 15

All the atoms of one element must have the same atomic number, but have different mass numbers
They combine with chemicals in the same way

Question 16

Radioisotopes

Answer 16

Have an unstable nucleus due to the forces of attraction from the neutrons are not enough to bind the nucleus together and outweigh repulsive forces (protons.
The nuclide may breakup or eject radiation energy
Radioactive

Question 17

Excitation

Answer 17

When an electron moves to a higher energy level and falls back quickly
Emission of electromagnetic radiation

Question 18

Ionisation

Answer 18

When an electron is ejected from an atom, another electron from a higher energy band falls down to replace the lost electron
Emission of electromagnetic radiation

Question 19

Explain the band theory

Answer 19

When two or more atoms are in close proximity, their energy levels become modified because their electrons are influenced by the electric fields of both atoms
If many atoms are closely spaced, energy bands are produced

Question 20

What are the three energy band categories?

Answer 20

Filled bands
Valence Bands
Conduction Bands

Question 21

What are forbidden gaps?

Answer 21

Separate energy bands
Contain no permitted electrons

Question 22

Filled band

Answer 22

Energy band bellow valence band
Possess a full complement of electrons

Question 23

Valence band

Answer 23

Highest energy band with electrons tied to a particular atom
Corresponds to the valence of a single isolated atom

Question 24

Conduction band

Answer 24

Energy band above valence band
Has free electrons

Question 25

Luminescence

Answer 25

Light emission
1-Fluorescence
2-Phosphorescence
3-Thermoluminescence

Question 26

Electron traps

Answer 26

In the forbidden gap, there are imperfections in the crystal structure to create extra energy levels
An electron that settles in the electron traps can only escape from it if it can gain sufficient energy to enable it to jump upwards into the conduction band (heated)

Question 27

Fluorescence

Answer 27

The instant re-emission of the absorbed energy
The energy of light emitted depends on the difference in the energy across the luminescence centre

Question 28

Luminescence centre

Answer 28

Return the electron to a ground state from an excited state

Question 29

Phosphorescence

Answer 29

The delayed re-emission of the absorbed energy, the emission of light continues for a while after initial stimulation of the phosphor has ceased

Question 30

Thermoluminescence

Answer 30

Prompted by the introduction of heat to phosphor to excite the electron following the material’s earlier absorption of energy from radiation
Electron trap is closer to valence band
Requires more energy