Chapter 8 - Radioactivity

Question 0

What did Pierre and Marie Curie discover?

Answer 0

Radioactivity carried an electrical charge

Isolated two new elements POLONIUM & RADIUM

Question 1

Who discovered radioactivity?

Answer 1

Henri Becquerel

Question 2

Define radioactivity

Answer 2

Spontaneous emission of one or more types of radiation,alpha,beta and gamma from unstable nuclei

Question 3

What are Alpha particles?

Answer 3

Positively charged rays. Consist of 2 protons and 2 neutrons, i.e helium nuclei 4He

Question 4

Penetrating ability and effects of Alpha particles?

Answer 4

Not very penetrating - stopped by a sheet of paper or 5 cm of air.

Effects - damaging to the DNA in cells - cause cancer

Question 5

What are Beta particles?

Answer 5

They are negatively charged rays. Occur when a neutron in an unstable nucleus is changed into a proton and an electron and this electron is EJECTED from a nucleus. (Give example)

Question 6

Penetrating ability of Beta particles?

Answer 6

Moderately penetrating - stopped by 5mm of aluminium

Question 7

What are gamma particles?

Answer 7

Neutral rays unaffected by electrical fields.

Gamma rays are High energy photons. -example - cobalt

Question 8

Gamma particle penetrating ability?

Answer 8

Very penetrating. Only stopped by a thick block of lead.

Question 9

What is transmutation?

Answer 9

When a new element is formed when alpha and beta particles are emitted.

Question 10

Chemical reactions VS Nuclear reactions

Answer 10

Chemical reactions deal with ELECTRONS being transferred or shared. The nuclei of the atoms stays the same.

Nuclear reactions only deal with the change in the NUCLEUS resulting in the formation of a new element.

Question 11

Nuclear fission

Answer 11

Large nuclei break up to form two smaller ones releasing a large quantity of energy.

Question 12

Nuclear fusion

Answer 12

Light nuclei join together to make a heavier one releasing energy.

Question 13

Define Half Life

Answer 13

The TIME taken for HALF of the nuclei in any given sample to DECAY

Question 14

What is a radioisotope?

Answer 14

A radioactive isotope

Question 15

Outline 3 uses of Radioisotopes

Answer 15

1) Medicine: radiotherapy- gamma rays from cobalt 60 are used to kill cancerous tissue.
2) Food Irradiation: irradiation with gamma rays kills pathogenic organisms in food causing no loss of flavour. Not suitable for all foods such as red meats etc as they turn brown.
3) Industrial uses: Am 241 is used in smoke detectors.

Question 16

Equation for alpha particles

226 Ra —- ??? + ?
88

Answer 16

226 Ra —- 222 Rn + Alpha
88 86

• 4 from larger number of atom
• 2 from smaller number

The new element + alpha

Question 17

Beta particle equation

14C —- ??? + ?
6

Answer 17

14C —- 14N + B
6 7

Larger number stays the same

Smaller number - +1

Question 18

Gamma ray equation

60CO — 60CO + Y

Answer 18

Stays the same but add a Y