Protons and neutrons are bound together to make the atomic nucleus

Protons have a positive electrical charge

Neutrons are neutral and have no electrical charge

It is a sub-atomic particle that can be found around the atomic nucleus.

It has a negative electric charge

Its mass is about 2000x less than a proton or neutron

Danish physicist Neils Bohr proposed the idea that electrons can be found around the nucleus in different energy levels or shells.

One cannot pinpoint the location of an electron, only about where it is in a specific energy level or shell

There are 7 electron shells (How many periods, or rows are on the periodic table?)

Each shell can hold a specific number of electrons• # of elements in the period = # of

electrons that shell can hold Q: How many electrons can the

2nd electron shell hold?• A: 8

1st Shell: 2 e-

2nd Shell: 8 e-

3rd Shell: 8 e-

Electrons fill each shell from the inside out. Ex: the 1st shell is filled first

Electrons in the outermost shell are called valence electrons.

They are involved in chemical bonding and reactions.

We will talk much more about these electrons when we talk about chemical reactions in later chapters.

A conceptual model of an atom

# of n and # of p are written in the nucleus (center circle)

# of e- are filled in each shell until it is full (How many can each shell hold?)• Once a shell is full, you

add another circle and continue.

Pick 3 elements from the first 18 elements, and create Bohr Diagrams for those elements.