Chemistry 10 Notes on Atomic Structure and Half Life.

Essay by penginHigh School, 10th grade September 2004

Atomic Structure

Atom: smallest particle of an element that can exist by itself

Main 2 things of atom

Orbitals

Electrons (-)

Nucleus

Nucleus = pea

Orbitals = the rest of the stadium

Relative Mass

Protons 1

Neutrons 1

Electrons 1/1839 (1/2000)

Not taken into account cuz it doesn't make a difference in total mass

Atomic # = # protons & electrons (if neutral)

Atomic Mass = # protons + # electrons

All atoms w/ same # of protons = 1 type of element

When mass is higher, usually more neutrons than protons

Neutrons are glue that hold the nucleus together

(+) charge of protons causes them to repel each other

Element so big that it isn't stable

Gives off protons & neutrons

Becomes more stable

Writing Elements

Write Symbol

Top left = atomic mass

Bottom left = atomic #

Sometimes omitted (implied by symbol)

Old Way of writing it

32-S = 32S

Isotope

Atom that has different # of neutrons

Still same Element

Different Forms of the same element

Atomic Mass = Average of all the different isotopes in nature

1 atom always had a whole # of neutrons

Example:

In nature, 75% of isotopes are 35Cl

25% are 37Cl

(75 * 35) + (25 * 37)

3550/100 = 35.5

<--Average

Brackets around the mass = always decaying

Hard to find out read Atomic mass

Half-Life

Amount of time it takes to decay to ÃÂ½

Used in C14 dating

Balancing Equations

# of atoms must be the same on both sides

Can't create or destroy matter

Easier to balance if you double odd #'s

Colours

Colour = transition middle

Salts & etc = white