P4 - Atomic Structure

Question 1

What is an isotope?

Answer 1

Form of an element with atoms that have the same number of protons but a different number of neutrons

Question 2

What was the plum pudding model?

Who created the plum pudding model?

Answer 2

Atoms were spheres of positive charge with tiny negative electrons stuck in them

J. J. Thomson (in 1897)

Question 3

What was the alpha scattering experiment?

Answer 3

. Positively charged alpha particles were fired at a thin sheet of gold foil
. Most went straight through but a few scattered

Question 4

What conclusions did the alpha scattering experiment lead to?

Answer 4

The alpha scattering experiment led to the discovery that…

. Most of an atom is empty space
. Atoms contain positively charged particles (protons) in the middle
. There is a concentrated mass in the middle - nucleus

Question 5

How was it discovered that the plum pudding model is wrong?

And what was the plum pudding model replaced with?

Answer 5

1909 - Ernest Rutherford conducted the alpha particle scattering experiment

1911 - Ernest Rutherford created the nuclear model of the atom

Question 6

What are the 4 types of radiation?

Answer 6

Alpha, Beta, Gamma, and neutron

Question 7

What is radioactive decay?

Answer 7

When the nuclei of some atoms are unstable they release radiation in order to become stable.

This is a random process.

Question 8

What is radiation?

Answer 8

Energy being transferred through waves or particles from a source.

Question 9

What is nuclear radiation?

Answer 9

Energy being transferred through waves or particles from a nucleus.

Question 10

What is ionising radiation?

Answer 10

Energy being transferred through waves or particles from a source, turning atoms into ions through the process.

Question 11

What is alpha radiation?

Answer 11

A particle made of 2 protons and 2 neutrons, the same as the nucleus of a helium atom.

Represented by α.

Question 12

What is beta radiation?

Answer 12

When a neutron splits and turns into a proton.
A high energy electron is released as a side product.

Represented by β.

Question 13

What is gamma radiation?

Answer 13

An electromagnetic wave that gets rid of excess energy.

Represented by γ.

Question 14

Why does beta decay not change an atom’s mass number?

Answer 14

The number of neutrons decreases by 1 and the number of proton increases by 1.

Question 15

Describe alpha radiation?

• penetration power - what it is stopped by
• ionising power
• range in air

Answer 15

Weakly penetrating - stopped by paper

Highly ionising

Range in air: 5-6cm

Question 16

Describe beta radiation?

• penetration power - what it is stopped by
• ionising power
• range in air

Answer 16

Moderately penetrating - stopped by a thin 2-3mm sheet of aluminium

Moderately ionising

Range in air: 1 metre

Question 17

Describe gamma radiation?

• penetration power - what it is stopped by
• ionising power
• range in air

Answer 17

Highly penetrating - stopped by 1m concrete or thick sheet of lead

Weakly ionising

Range in air: unlimited

Question 18

What is the mass and charge of alpha radiation?

Answer 18

Mass: 4
Charge: +2

Question 19

What is the mass and charge of beta radiation?

Answer 19

Mass: 0
Charge: -1

Question 20

What is the mass and charge of gamma radiation?

Answer 20

It does not have a mass or change because it is an electromagnetic wave

Question 21

What is activity?

Answer 21

The number of radioactive nuclei that decay every second

Question 22

What is activity measured in?

What device is used to measure activity?

Answer 22

Becquerels (bq)
1 bq = 1 nucleus decaying every second.

Geiger counter
(Geiger-müller tube)

Question 23

What is half life?

Answer 23

The time taken for half of the radioisotope to decay

Question 24

What are the two reasons we measure half life?

Answer 24

1- Radioactive decay is RANDOM, so we cannot tell when any particular nucleus will decay but we do know that half of them will decay in a certain time.

2- The half life is always the same for any particular radioactive isotope. Whereas the time take for ALL the radioisotopes in a sample to decay would depend on how many you had to begin with.

Question 25

How does the arrangement of electrons change with the absorption of electromagnetic radiation?
Why does this happen?

Answer 25

Electrons move further away from the nucleus when electromagnetic radiation is absorbed, due to a higher energy level.

Question 26

When absorbing electromagnetic radiation, why do electrons move closer to the nucleus?

Answer 26

Lower energy level

Question 27

What is Relative Atomic Mass (RAM)?

Answer 27

The average mass of the atoms in an element

Question 28

What is the equation for Relative Atomic Mass (RAM)?

Answer 28

(Mass of isotope 1 x % of isotope 1) + (Mass of isotope 2 x % of isotope 2)
———————————————————
100

Question 29

What is radioactive contamination?

Answer 29

The unwanted presence of materials containing radioactive atoms on other materials

Question 30

What is irradiation?

Answer 30

The process of exposing an object to nuclear radiation

Question 31

What are some of the symptoms of a person exposed to radiation?

Answer 31

Cataracts in the eyes
Cancer
Sterility
Radiation burns on skin
Damaged immune system
Vomiting
Bleeding