Atomic Number & Mass Number• Atomic number = the number of

protons

• Mass number = the number of nucleons (protons & neutrons)

• A neutral atom has the same number of protons and electrons.

Oxygen atom

Sodium atom

Aluminium atom

Copper atom

Platinum atom

Gold atom

Lead atom

Radium atom

Uranium atom

Use your periodic table to find…1. The number of protons in a carbon atom2. The number of protons in a sodium atom3. The number of neutrons in a sodium atom4. The number of protons in a copper atom5. The number of neutrons in a copper atom6. The number of protons in a lead atom7. The number of neutrons in a lead atom8. The number of electrons in a lead atom

How many neutrons are there in a chlorine atom?

Some chlorine atoms have 18 neutrons.Some have 19…They are “isotopes” of chlorine.(Chlorine–35 and Chlorine-36)

Example: Carbon IsotopesIsotopes Protons Electrons NeutronsCarbon-12 6 6 6

Carbon-13 6 6 7

Carbon-14 6 6 8

WORKSHEET ONE – first page only

Turning copper into gold?

Three types of Nuclear Reactions

1. Radioactive decay

2. Fusion

3. Fission

Uranium atom

Alpha Radiation (α particle)• High-speed helium nucleus (+ve charge)• two protons & two neutrons• Can travel up to 10% of speed of light.• Range: a few centimetres• Can be stopped by a sheet of paper.• Can cause serious harm but cannot

penetrate skin.

Beta Radiation (β particle)• High-energy electron (-ve charge)• Can travel up to 90% of speed of light.• Range: about 30 cm• Can be stopped by a sheet of

aluminium about 5 mm thick.

Gamma Radiation (γ Ray)• Electromagnetic radiation with very high

energy• Occurs as a result of a nucleus being left

in a very excited state immediately following other types of radioactivity.

• Travels at the speed of light.• Can penetrate through several

centimetres of dense metal such as lead.

Finish WORKSHEET ONE