Atoms

Atoms are made up of protons, neutrons and electrons

Atoms are unique to each element.

The outermost electrons are called valence electrons

Label the Atom

ElectronsValence electrons are important in deciding

which atoms can bond (chemically combine to form a new substance)

All atoms want to have 8 valence electrons. The only exceptions are H and He.

Hydrogen and Helium only want 2 valence electrons.

CompoundsElements combine with other elements to get

the 2 or 8 valence electrons.

When two elements chemically combine to form something new the result is called a chemical compound.

When a compound is formed people say a bond was formed between the elements.

Compounds

When two or more elements combine or exchange valence electrons they bond or form a molecule

This is a chemical change because a new substance is formed.

You can see compounds form in chemical reactions or changes.

Learning Launch

• Turn in homework to box (purple sheet) AND get out periodic table

• LL 10/11/2013

• Get out notes from yesterday (white sheet)

Find the number of Find the number of Find the number of Protons for… Neutrons for… Electrons for…Xe _______ He _________ O _______K _______ Si _________ Cl _______Fe _______ I __________ B _______Ne _______ Mg ________ Na ______

So how and why do these electrons move?

1. The nucleus (center) of the atom is surrounded by swirling electrons.

2. The electrons move on invisible rings called energy levels, orbitals or shells.

Lets look Each orbital or energy level canonly hold a certain number ofelectrons…

3. The first energy level around the nucleus can only hold a maximum of 2 electrons…

it is not strong enough to hold anymore…

4. Which elements on the periodic table only have 1 or 2 total

electrons?Hydrogen and HeliumREMEMBER!!! Atomic number = number of protons = number

of electronsSo.. You look at the top number to find the total

number of electrons in 1 atom of that element… and the answer to our question is…

They look like this.

Hydrogen (H) Helium (He)

Atomic Number - 1 Atomic number - 2

1 electron 2 electrons

Lets fill in some info

HydrogenAtomic number: __1___

Has __1____ electron and __1____ proton.

In Group/Family number_1__

In Period: __1___

Has ___1___ energy level

HeliumAtomic number: ___2___

Has __2___ electrons and ___2___ protons.

In Group/ Family number __18__

In period _____1___

Has ___1_____ energy level.

What next…

7. Once the first energy level has two electrons on it, it is full, so if an atom has more than 2 electrons, it needs another energy level…

Lets look at Lithium.Lithium – atomic # 3

LithiumLithium has an atomic number of..

That means that is has protons and electrons.

Can all of Lithium’s electrons fit on one energy level??

NOOOOO!

Because the first energy level can only hold a max. of 2 electrons…

An atom of Lithium (Li) must have two energy levels to fit all3 electrons.

It looks like this

Fill in info on Lithium

Atomic number: __3__Has __3____ electrons and __3____ protons.In Group/Family number_1__Has _1____ valence electronIn Period: __2___Has _2___ energy level