Topic 4 : Atomic Stucture

Question 1

What two types of particles make up an atom’s nucleus?

Answer 1

Protons and neutrons

Question 2

True or false? The radius of the nucleus is less than 1/10 000 of the radius of the atom

Answer 2

True (the nucleus is tiny, but it contains most of the mass of the atom)

Question 3

Describe the plum pudding model of an atom

Answer 3

In the plum pudding model, atoms are spheres of positive charge with tiny negatively charged electrons stuck in them

Question 4

How did Neils Bohr adapt the nuclear model of the atom?

Answer 4

Bohr suggested that electrons orbit the nucleus at specific distances called energy levels

Question 5

True or false? Different isotopes of an element will have the same number of neutrons but a different number of protons

Answer 5

False (different isotopes of an element will have the same number of protons but a different number of neutrons)

Question 6

An atom has 22 protons and 19 neutrons. How many electrons does it have?

Answer 6

22 electrons (an atom has the same number of electrons as protons)

Question 7

True or false? An alpha particle is the same as a hydrogen nucleus

Answer 7

False (an alpha particle is the same as a helium nucleus, not a hydrogen nucleus)

Question 8

What are gamma rays?

Answer 8

Short wavelength electromagnetic radiation emitted by the nucleus of the atom

Question 9

What is a beta particle?

Answer 9

A fast-moving electron (a beta particle is released by the nucleus as a neutron turns into a proton)

Question 10

Why do some atomic nuclei undergo radioactive decay?

Answer 10

Unstable atomic nuclei decay to become more stable

Question 11

Wha is meant by the ionising power of radiation?

Answer 11

Ionising power is a measure of how easily ionising radiation can remove electrons from Atoms

Question 12

What type of radiation can pass through a sheet of paper or a sheet of aluminium sheet, but cannot pass though a thick sheet of lead?

Answer 12

Gamma radiation

Question 13

A nucleus emits a gamma ray. What happens to the mass number of the atom?

Answer 13

The mass number and the charge stay the same

Question 14

Explain how this nuclear equation shows that a neutron has been converted to a proton during the decay

Answer 14

The proton number has increased, but the mass number has not changed. So a neutron must have become a proton during the decay

Question 15

Define half life in terms of the number of nuclei of an isotope in a sample

Answer 15

The half life of a radioactive isotope is the time taken for the number of nuclei of that isotope in a sample to halve

Question 16

True or false? It is possible to predict exactly how long it will take for a certain radioactive nucleus to decay

Answer 16

False (radioactive decay is a random process)

Question 17

True or false? Half life is the time taken for the count rate of a sample to halve

Answer 17

True

Question 18

How many half lives would it take for the number of nuclei of a radioactive isotope to decrease to an eighth of its initial value

Answer 18

3 half lives

Question 19

Give one natural cause of background radiation

Answer 19

Air, food, rock, cosmic rays

Question 20

True or false? In nuclear fusion, some of the mass of the nuclei being fused together is converted to energy

Answer 20

True

Question 21

True or false? A nuclear reactor uses an uncontrollable chain reaction to maximise the energy released from the fuel

Answer 21

False (uncontrolled chain reaction cause an explosion as lots of energy is being released at once)