Chemical Reactions

• Involves the change of one or more substances into new substances

• Atoms are rearranged but their identities do NOT change

• The reaction involves the atom’s electrons only

Nuclear Reactions

• An atom of one element changes into an atom of another element

• The identities of the atoms do change• Involves a change in the atom’s nucleus• Don’t occur that often in nature

because many atoms have already decayed (undergone nuclear rxns) into stable atoms during Earth’s long history

Radioactivity• Some substances spontaneously emit

radiation – it requires no energy• Occurs because an atom’s nucleus is

unstable or overcrowded• The atom gains stability by losing energy

or emitting radiation (like a pencil tipping over)

• An atom continues to be radioactive and undergoes decay until its nucleus becomes stable

Radioactive Decay• 3 main types of radiation are emitted

during radioactive decay (alpha, beta & gamma) – all 3 have energy & 1 has mass

• The rays & particles emitted are known as RADIATION

• The process of emitting them is radioactivity or radioactive decay

Nuclear Stability

• The prime factor in achieving nuclear stability is for an atom to have a favorable neutron to proton ratio in its nucleus

• Too high or too low leads to instability and nuclear decay

Alpha Radiation

• Radiation made up of alpha particles• Each particle has 2 p+ and 2 no, so

has a +2 charge and a mass of 4 amu• Basically a helium atom without

electrons• The biggest and slowest of the three

types, so it penetrates into matter the least

Beta Radiation

• Consists of the fast moving electrons called beta particles

• Has no mass but has a -1 charge• Smaller with more energy than alpha

particles, so penetrate further• A beta particle breaks off of a neutron

and leaves behind a proton

Gamma Radiation• It’s high energy radiation that has no

mass, and no electrical charge• Highest energy of the 3, so penetrates

the most & potentially the most damaging

• Accounts for most of the energy lost during radioactive decay

• Emission of gamma rays alone does not result in a new atom but usually accompanies beta & alpha radiation

Nuclear Equation• An equation that shows what

happens during a nuclear reaction• Both the mass number and atomic

number is conserved• Examples:

Polonium-210 undergoes alpha decay

Nuclear Equation• Both the mass number and atomic

number is conserved• Examples:

Thorium-234 undergoes beta decay

Nuclear Equation• Both the mass number and atomic

number is conserved• Examples:

Uranium-234 undergoes alpha decay

Nuclear Equation• Both the mass number and atomic

number is conserved• Examples:

Bismuth-214 undergoes beta decay

Nuclear Equation• Both the mass number and atomic

number is conserved• Examples:

Uranium-238 undergoes alpha decay accompanied by 2 gamma rays

Did you know?• Radon exists only as a by-product of the

radioactive decay of uranium-238.• Radon will further decay into radioactive

isotopes of polonium, bismuth and lead.• All 3 of these isotopes are heavy metals that

are difficult to remove from the human body.• It’s estimated 10,000 to 20,000 lung cancer

deaths per year are caused by exposure to radon.

• Radon is usually found in soil or building materials.