1.2 - Basic Ideas About Atoms

Question 1

(a)

Atomic structure

Answer 1

**Proton: ** relative mass -1, relative charge - +1
Neutron: relative mass -1, relative charge- 0
**Electron: **relative mass-
negligible, relative charge -1

Question 2

(a)

Atomic number

Answer 2

number of protons

Question 3

(a)

Mass number

Answer 3

sum of protons and neutrons

Question 4

(a)

Isotopes

Answer 4

Atoms of the same element can have different numbers of neutrons. These are called isotopes.

Question 5

(a)

Alpha (α) particles

Answer 5

positively charged helium nuclei, mass of four units, stopped by a piece of paper, strongly ionising

Question 6

(a)

Beta (β) particles

Answer 6

Negatively charged electrons, negligible mass, stopped by 0.5 cm of aluminium

Question 7

(a)

Gamma (γ) radiation

Answer 7

very high energy electromagnetic
radiation, > 2cm of lead required to stop it, weakly ionising.

Question 8

(a)

Alpha decay (α)

Question 9

(a)

Beta decay (β)

Question 10

(a)

Positron emission (β+
decay)

Question 11

(a)

Electron capture (inverse β decay)

Question 12

(b)

behaviour of α-radiation in electric and magnetic field and relative penetrating power

Answer 12

α-particles are positive, heavy and slow moving and are attracted slightly to the negative plate
of an electric field.

Question 13

(b)

behaviour of β-radiation in electric and magnetic field and relative penetrating power

Answer 13

β-particles are light and fast moving and show considerable deviation towards the positive plate of an electric field.

Question 14

(b)

behaviour of γ-radiation in electric and magnetic field and relative penetrating power

Answer 14

γ-radiation is electromagnetic radiation of short wavelength and is unaffected by an electric
field.