Matter

Anything that takes up space and has mass

Composed of elements

Element

Substance that can not be broken down to other substances by chemical reactions

Compounds

Two or more elements combined in a fixed ratio

What is nucleus composed of?

Protons (p) +

Neutrons (n) 0

Electrons (e-) -

What is a Dalton?

1 Dalton ~ to 1 amu (1.7x10^-24)

What is the Atomic Mas?

What is Mass Number?

Atomic mass is at the top of the element symbol

              atomic mass --> _¹⁶
                                        O <-- Element symbol

           atomic number --> _⁸

Isotopes

When mass of some atoms can vary (some atomic forms have more neutrons than others

Considered stable if their nuclei do not have a tendency to lose particles

Radioactive Isotopes

unstable and nuclei decays/gives off particles and energy

are used in medicine, research, energy, and bombs

Energy Level

Determines the disstance of an electron from the nucleus