The AtomWhat defines the property of a substance

WHAT MAKES UP MATTER? The one thing that makes up all things

in the universe is:

ATOMS

WHAT ARE ATOMS?Atom: smallest part of an element that can be identified as the element. (can be found on periodic table)

For instance water (H2O), it can be broken down to 2 hydrogen atoms and 1 oxygen atom.

DEMOCRITUS

DEMOCRITUSDemocritus: the first person to suggest the idea of atoms.He was a Greek philosopher who lived more than 2400 years ago.He used the word “atom” which means cannot be divided.

JOHN DALTON

DALTON’S ATOMIC THEORYIn the early 1800’s, stated an atomic theory of matter.

Dalton’s theory was the beginning of the modern theory of atoms.

DALTON’S ATOMIC THEORY•All elements are composed of atoms. Atoms cannot be divided or destroyed.•Atoms of the same element are exactly alike.•Atoms of different elements are different.•The atoms of 2 or more elements can join together to form compounds.

TODAYWe know that atoms define the

chemical properties of different substances

Atoms can be divided into smaller particles

These particles help to define the characteristics of the atom

PARTS OF THE ATOMElectron: negatively charged particle.

Neutron: neutral particle.Proton: positively charged particle.

Nucleus: center, or core, of an atom.

PARTICLES OF THE ATOMProton:

Mass: 1.673 x 10-24 gAtomic mass: 1Charge: +1Location: Nucleus

PARTICLES OF THE ATOMNeutron:

Mass: 1.675 x 10-24 gAtomic mass: 1Charge: 0Location: Nucleus

PARTICLES OF THE ATOMElectron:

Mass: 9.11 x 10-28 gAtomic mass: 0Charge: -1Location: Space around the

nucleusThe electron is so small compared

to the other particles, it is given an atomic mass of 0

PARTS OF THE ATOM

HOW DO ELECTRONS ORBIT THE NUCLEUS

In your notebook, draw how you think the electrons go around the nucleus

In addition, HOW many elections go in each section?

BOHR MODEL The model most of you suggested is

called the Bohr model of the atom Using the periodic table, you can figure

out how many electrons “orbit” in each “shell” of the atom

We will be discussing the “electron configuration” later in the quarter