RADIOACTIVITY&

HALF-LIFE NOTES

Isotope The same element with a

different number of neutrons: EX- C-12(6n°), C-13(7n°) & C-14 (8n°) 12.001= the Real Mass: An

average of all the isotopes of that element.

Radioactivity

The nucleus of an atom breaks down and emits radioactive particles:

EX- Alpha- slow, absorbed by a substance thicker than paper

Beta- almost the speed of light-more penetration: can go through thin copper sheet

Gamma- travels at the speed of light and can penetrate lead. 299,792,458 m/s!!

Uses in Industry: Check the thickness of paper and plastic, keep food fresh, radioactive tracing (track substances through the body) and radiotherapy (kills cancer cells)

Half-life The amount of time it takes for half of the

atoms in a radioactive sample to decay. EX- C14= 5,700 yrs. & Be11= 13.81s The half-life for a given isotope is always

the same. It doesn’t depend on how many atoms you have or how long they have been sitting around!

EX- Be11(changes to B11) 16g---- 8g ----- 4g ---- 2g

13.81s 13.81s 13.81s 3-Half-lives have passed!!