Elements and Compounds

Warm Up Activity This picture show the atoms that are

present in the air.

1. Which ones are elements?

2. How can you tell?

What do we call these

things?

An Atom

3 Atoms

What do we call these

things?

6 Atoms which

happen to be of 3

different elements

What do we call these

things?

A Molecule

• We don’t call it “2 atoms joined

together” we say it is one molecule.

• Since the atoms are the same, it is

also an element, not a compound.

What do we call these

things?

A Molecule of a

compound

2 molecules of a

compound

* Notice that these

molecules have

different atoms in

them, so they are

compounds, not

elements.

Some of the elements in air go around

as single atoms (such as argon).

Or as molecules such as oxygen.

Compounds go around as molecules.

Since there is just one atom, you

would write: Ar

Since there are two atoms of the

same element, you would write O2

Since there are different elements,

you would list both: H2O.

Ar

O H

H

Since there’s 2

oxygen atoms, you

write a “2” after the

O

O

O

If there’s just one

atom, don’t put a

number after it!

( Gas)

One Element

This one likes to go round

in pairs as a gas.

(molecules)

This a COMPOUND of

two different elements

Notice there are

two different

types of atoms

joined together.

That’s what

makes this a

compound.

Element or

Compound?

Element

Element or

Compound?

Compound

Element or

Compound?

Compound