Atomic Structure & Periodic Table, Radioactivity

Question 1

Neutral atom

Answer 1

The total number of electrons always equals the number of protons in the nucleus.

Question 2

Relative Atomic Mass (RAM)

Answer 2

• RAM is usually NOT whole numbers and refers to the “average” mass of an atom for that element.
• Rounding the RAM to the nearest whole number gives the mass number of the most common isotopes of the element.

Question 3

Isotopes

Answer 3

Isotopes of an element are atoms that contain different numbers of neutrons in the nucleus. Many Isotopes are unstable and decompose by radioactive decay.

e.g. 12 13 14
C C C
6 6 6

Question 4

Radioisotopes

Answer 4

A radioactive isotope is an atom with an unstable nucleus that spontaneously decays and emits radiation until the nucleus becomes stable.

Question 5

Alpha

Answer 5

Composition: 2 protons + 2 neutrons
Charge: 2+
Range in Air: Few cm
Range in skin: nil
Stopped by: Skin, Paper, Clothing

Question 6

Beta

Answer 6

Composition: High energy electrons from the breakdown of neutron (nucleus)
Charge: 1-
Range in Air: Few meters
Range in Skin: Few mm
Stopped by: Bone, Wood, plastic

Question 7

Gamma

Answer 7

Composition: EM radiation (pure energy)
Charge:0
Range in Air: Up to 2 km
Range in Skin: Right through body
Stopped by: Lead, thick concrete

Question 8

Direct radiation damage

Answer 8

occurs when ALPHA or BETA particles actually collide with cell molecules causing them to break.

Question 9

Indirect radiation damage

Answer 9

occurs when the high-energy radiation emitted from the nucleus strips electrons from atoms/molecules as it passes close by and creates charged particles or ions within the cell. This can be referred to as Ionizing radiation.

Question 10

Half-life radioisotopes

Answer 10

Radioisotopes with a short half-life are decaying faster than those with a half-life measured in years; the shorter the half-life, the more unstable the radioisotope.