Radioactivity

Isotopes and the Atomic theory

Radioactivity

• The release of high-energy particles and rays of energy from a substance caused by changes in the nuclei of the atom

Uses• Medical diagnostic equipment and treatment,• Electricity

Natural Background Radiation

• Fast moving particles or waves that are found in the natural environment

Radiation• High-energy rays and particles emitted by

radioactive sources– eg,. Microwave, radio waves, X-rays, Gamma rays

Isotopes and Mass Number

Isotopes: Atoms that have the same number of protons but different number of neutrons

Eg. Na with 12 neutrons or Na with 11 neutrons

How do we determine if an atom is an isotope

• We must be able to calculate the number of neutrons

Remember atomic mass = protons + neutrons

neutrons = atomic mass – atomic number

Representing isotopes

You will need to write a standard atomic symbol:• Symbol (K)• Atomic number (19)• Atomic mass (39)

Eg

39K

19

Writing out names of isotopes

• Write out atom name then a dash and then the atomic mass given (may be different then one on the periodic table)

Eg Carbon-12, or Carbon-14

Assignment

Questions 1-4