ATOMIC STRUCTURE REVIEW AND HISTORY OF THE ATOMIC

MODEL

Atomic Theory

Matter

All matter is made up of tiny particles called atoms

Atomic Structure

+ +

+

+

proton

neutron

electron

nucleus

Atom An atom is made up of

Protons + Neutrons 0

Electrons -

Protons Neutron Electron

Electriccharge

Location in the atom

positive

No charge / neutral

negative

In nucleus

In nucleus

Outside nucleus

How big is an atom?

The typical atom is about One ten-billionth of a meter in

diameter

The average nucleus of an atom is about One million billionth of a meter in diameter

http://www.youtube.com/watch?v=yQP4UJhNn0I#t=188

The mass of an atom

The nucleus is made up of the protons and neutrons

The protons and neutrons have about the same mass

The electrons surrounding the nucleus have a mass about one two-thousandths the mass of the protons or neutrons

Most of an atoms mass is in the nucleus

Size of an atom

The subatomic particles of the atom are tiny compared to the atom as a whole

The majority of an atoms volume consists of empty space

There are more than a million million billion atoms in a sing drop of water

http://youtu.be/qxXf7AJZ73A

The History of the Atomic

Theory

Democritus Greek philosopher in 440 bc

Was the first to proposed the existence of atoms

“Atomos” meaning “not to be cut”

John Dalton

British chemist 1803Atomic Theory – He

came up with the theory that all substances were made of atoms

Atoms were small, hard, dense spheres that could not be created, destroyed, or altered

Dmitri Mendeleev

Known as the father of the present day periodic table

Organized the elements (each type of atom) by similar properties in 1869

J. J. Thomson British scientist 1898

Proposed that atoms themselves were made of smaller particles .

He discovered that atoms contained negatively charged particles, but did not know their location

J. J. ThomsonTheorized the

negatively charged particles were spread evenly throughout the positively charged material

Thomson’s model of the atom was called the “plum-pudding” model

Ernest Rutherford1911 a former

student of Thomson's

Proposed that atoms had a dense, positively charged nucleus surrounded by electrons

Niels Bohr1913 Danish

scientist

Said that electrons revolve around the nucleus in circular paths, called orbits

And that electrons could only exist in certain orbits and at certain energy levels

http://youtu.be/wCCz20JOXXk

Today’s modelelectron cloud model

Bohr’s model was an important stepping stone to today’s, which was developed in the 1920’s

Electrons surround the nucleus, traveling not in prescribed paths but in regions of various thicknesses called clouds

http://youtu.be/kYkD-dcupAU

Law of Conservation of Matter

Matter (mass) cannot be created or destroyed but it can be rearranged.

The mass of the reactants must be equal to the mass of the products.

The mass of the substance you end with must be equal to the mass of the substances you begin with.