P7.3 - Changes In The Nucleus (Finished)

Question 1

What is the atomic number of an element and mass number?

Answer 1

The atomic number is the number of protons in an atom, and mass number is the number of protons + neutrons in an atom’s nucleus

Question 2

What are isotopes?

Answer 2

Isotopes of an element are atoms with the same number of protons but different numbers of neutrons

Question 3

All elements have different isotopes, but why are only a few found?

Answer 3

Usually an element has only one or two stable isotopes

Question 4

What is radioactive decay?

Answer 4

Radioactive decay is the process of unstable isotopes decaying into other elements, giving out radiation as they try to become more stable

Question 5

Appart from alpha, beta and gamma radiation what can unstable isotopes also give out and why?

Answer 5

Unstable isotopes can also give out neutrons as they decay as they rebalance their atomic and mass numbers

Question 6

What is ionising radiation?

Answer 6

Ionising radiation is radiation that knocks electrons off atoms creating positive ions

Question 7

What is the ionising power of a radiation source?

Answer 7

The ionising power if a radiation source is a measure of how easily it can knock electrons off atoms

Question 8

Give the properties of alpha radiation?

Answer 8

• Alpha particles are a helium nucleus (2proton, 2neutron)
• They can only travel a few cm in air and are absorbed by a sheet of paper
• They are strongly ionising

Question 9

Why are alpha particles strongly ionising?

Answer 9

Due to their size

Question 10

What are the properties of beta radiation?

Answer 10

• It is a fast moving electron released by the nucleus
• They have a few m range in air and are stopped by 5cm aluminium sheet
• They are moderately ionising

Question 11

Give the properties of gamma radiation?

Answer 11

• Can be stopped by a thick lead sheet but travels unlimitedly in air (spreads out)
• They are weakly ionising
• They are waves of electromagnetic radiation

Question 12

When an atom emits an alpha particle how does it’s atomic and mass numbers change and why?

Answer 12

It’s atomic number goes down by 2 and mass number down by 4, as an alpha particle is 2 protons , 2 neutrons,

Question 13

How does an atom’s atomic and mass numbers change when a beta particle is emitted and why?

Answer 13

The atomic number goes up by 1 (charge increases) and mass number doesn’t change. As in beta decay a neutron turns into a proton releasing a fast moving electron (beta radiation)

Question 14

How do gamma rays emitted change the mass and atomic no of an atom?

Answer 14

They don’t