Elements

*organized on the Periodic Table of Elements

*periodic= occuring in a predictable pattern

The Ancient Beliefs 440 BC

They thought there were

4 elements:

•Fire

•Water

•Wind

•Earth

Elements

• are substances that cannot be changed into simpler substances by chemical reactions.

• There are about 118 elements found on Earth (only 92 occur naturally).

Starts with metals

Metals-Metalloids--Nonmetals- Noble Gases

An atomis the smallest part of an element

An atom is made up of:

Protons

Neutrons

Electrons

Key for the Periodic Table

CCarbon-------Element name

6 -------------atomic number

------Element symbol

12.011------atomic mass

Subatomic particlesparticle charge location Mass

(in amu’s)

Proton + In nucleus 1

neutron No charge In nucleus 1

electron negative In orbit around the nucleus

1/1836

Video on atoms-listen

An atom of Lithium

*The atomic # of Lithium must be 3

*The mass of an atom of Lithium MUST be 7. (4+3)

An atom of Sodium Na

• The atomic # of Sodium must be 11

• *The mass of an atom of Lithium MUST be 23. (11 + 12)

The atom and the Periodic Table

• The atomic # = the # of protons• The mass of the atom is:• (# protons) + (# of neutrons)• Assume the # of electrons = # protons

Drawing atoms:

• Let’s draw an atom of:

Carbon

• Let’s draw an atom of:

Fluorine

Atom comes from the Greek word

atomos

• Atomos in Greek means INVISIBLE

• Scientists used to think that the atom was NOT made of any smaller particles

• It wasn’t until 1897 that scientists realized that atoms are made up of smaller particles

Draw these on your own

• Helium

• Potassium

• Oxygen

• Hydrogen

Molecules and atoms

• Molecules are made up of atoms. Water is a molecule with 2 Hydrogen atoms and and 1 Oxygen atom.

• How many atoms are in:

• CO2

• H2O2

• O2

What are they?

Metals

• Good conductors of heat and electricity

• Good at giving up electrons

• Malleable and ductile• Lustrous

Non-Metals• Poor conductors

therefore, good insulators• Good at taking electrons• Brittle (break easily)

Nuclei of a Helium atom and of a Lithium atom