Atoms and MoleculesUnit 4A

The Building Blocks of Matter

All matter is formed by:

• Atoms• Molecules

• Molecules are groups of different types of atoms bonded together.

Subatomic Particles(Parts of an Atom)

• Proton• Electron• Neutron

• Measured by AMU’s• Atomic Mass Unit

Parts of an Atom

Particle Location Charge Mass

P+ Nucleus + 1 amu

e- Outside - 0 amu

N0 Nucleus 0 1 amu

Parts of an Atom• Atoms are mostly empty

space.

Ex: If you put a golf ball in the middle of a football stadium (nucleus), the electrons would be WAY up in the nosebleed sections.

Atomic Models

• The current model is Electron Cloud, but it is complicated.

So… • We will be using the Bohr Model.

The Bohr Model• Electrons surround the nucleus in different energy levels.

e-

e- e-

e-

e-

e-

e-

e-

e-

e-

P+ N0

Elements• Elements = only 1 kind of atom

• The # of PROTONS in that element tell us which element it is •Listed on P.T. as atomic number

• The Atomic Number tells us the number of Protons an atom has

• It also tells us how many electrons a neutral atom has

• REMEMBER - APE

Isotopes

• Isotopes – elements that have the same # of protons and a different # of neutrons

• Isotopes have different masses.

Atomic Mass

• Mass number = the mass of one atom

• Atomic mass = the average mass of all isotopes of that element.

Mass # = #P+ + #N0

Isotope Notation

C12

6C

6

13

C14

6

Mass #

Atomic #