Atoms and Radiation

Question 1

What does an atom consist of?

Answer 1

a small dense central nucleus composed of protons (positive) and neutrons (no charge), surrounded by electrons (negative)

Question 2

An atom will always have the same..

Answer 2

number of electrons and protons - equalling an atom with a charge of 0

Question 3

What does atomic number =?

Answer 3

The number of protons (and electrons) - this tells you the element

Question 4

What does mass number =?

Answer 4

The number of protons + neutrons

Question 5

Proton relative mass?

Answer 5

1

Question 6

Neutron relative mass?

Answer 6

1

Question 7

Electron relative mass?

Answer 7

1/2000

Question 8

Nuclear notation?

Answer 8

http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/nucnot.html

Question 9

What is an isotope?

Answer 9

Isotopes are forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties

Question 10

Democritus? Time?

Answer 10

460 BC - Suggested matter can’t be cut smaller forever, called the smallest particle of matter: The Atom - thought atoms had different shapes and sizes

Question 11

John Dalton? Time? (5)

Answer 11

1766

1. Believed all matter is made of tiny particles called the atoms
2. Atoms are indivisible and indestructible
3. Atoms of the same element are identical
4. Atoms of different elements are different
5. Atoms combine in simple whole number ratios to form compounds

Question 12

J.J. Thompson? Time?

Answer 12

1856 - Worked with cathode - Ray tubes, credited with the discovery of the electron - knew it was negative, also came up with the plum pudding model

Question 13

Plum Pudding model?

Answer 13

Negative electrons embedded in a volume/cloud of positive charge

Question 14

Ernest Rutherford? Time?

Answer 14

1871
1. Famous gold foil experiment in which alpha particles were fired at a tin gold foil piece
He found that
1. Almost all alpha particles went straight through - most of the atom is empty space
2. A few particles were deflected through at a smaller angle - small positively charged nucleus reflected alpha particles
3. 1 in 8000 were deflected backwards - these were the particles that “hit” the nucleus

He concluded that most of the atom was empty space, however, there was a very small very dense positively charged nucleus with electrons - negatively charged - floating around.

Question 15

Atoms of some substances are unstable and radioactive. This means..

Answer 15

they may give off alpha/beta particles, or gamma rays

Question 16

They “want” to be stable (balanced) so to try and achieve this, they…

Answer 16

emit energy (or particles) in the form of radiation

Question 17

How many types of radiation are there?

Answer 17

3: alpha decay, beta decay and gamma decay

Question 18

Alpha decay?

Answer 18

an alpha particle consists of 2 protons and 2 neutrons (identical to the helium nucleus)
Emitted by some isotopes of the heaviest elements

Question 19

Beta decay?

Answer 19

A beta particle consists of a high speed electron
They are emitted by isotopes that have too many neutrons
One of these neutrons decay into a proton and a high speed electron - the protons remains in the nucleus but the electron is emitted as a beta particle

Question 20

Gamma decay?

Answer 20

Gamma decay is the emission of a high frequency EM waves from an unstable nucleus, gamma radiation often occurs after a nucleus has emitted an alpha or beta particle

Question 21

The decay of an unstable nucleus is…

Answer 21

random. we know it’s going to happen but can’t say when, it cannot be affected by temperature or pressure

Question 22

Decay?

Answer 22

a particle or energy leaving the nucleus

Question 23

What happens to the mass number and atomic number of an atom when an alpha particle is released?

Answer 23

The mass number decreases by 4, the atomic number decreases by 2

Question 24

What happens to the mass number and atomic number of an atom when a beta particle is released?

Answer 24

The mass number stays the same, but the atomic number increases by 1.

Question 25

What happens to the mass number and atomic number of an atom when gamma rays are emitted?

Answer 25

The mass and atomic number stay the same

Question 26

Order of radiation from most to least ionizing?

Answer 26

1. Alpa
2. Beta
3. Gamma

Question 27

Why is alpha the most ionizing form of radiation?

Answer 27

Alpha particles has the highest charge (+2) and is large so will come near many electrons and attract them away from the outer shell of the atom

Question 28

Why is beta 2nd most ionizing form of radiation?

Answer 28

Beta particles have a small charge (-1) and are small, they will repel any electrons they come close too.

Question 29

Why is gamma decay the least ionizing form of radiation?

Answer 29

Gamma decay is a form of energy, if it hits an electron directly, it will give it the energy to escape its shell

Question 30

What is alpha decay stopped by?

Answer 30

Paper (also aluminium + lead)

Question 31

What is beta decay stopped by?

Answer 31

Aluminium (also lead)

Question 32

What is gamma decay stopped by?

Answer 32

Lead

Question 33

What is contamination?

Answer 33

When the radioactive source goes into the object

Question 34

What is irradiation?

Answer 34

The radioactive source goes outside the object. The object is exposed to rays from the source

Question 35

What is a Geiger counter?

Answer 35

A Geiger counter is an instrument used for detecting and measuring ionizing radiation.