Bell Ringer THINK BACK TO LAST CLASS & The History of the Atom! WITHOUT using your notes match the scientist to

the correct statement that describes his work.

Ernest Rutherford J.J. Thomson Schrodinger & Heisenberg

John Dalton Democritus Niels Bohr 1. _______________________________ proposed that all matter is made up of tiny particles called atoms (from the word that means "indivisible.") 2. _______________________________ suggested that electrons travel in well-defined paths. 3. _______________________________ discovered that atoms have electrons and thought that they were embedded in positively charged material. 4. _______________________________ proposed that matter is composed of atoms and the atoms of an element are identical. His Atomic Theory suggested that atoms can be thought of as being much like a small uniformly solid ball. 5. _______________________________ concluded that there is a small, dense, positively charged nucleus. 6. ______________________________ proposed that electrons travel in electron clouds.

Unit 3: Chemistry. Introduction to Atoms.

How big is an atom?

On average the diameter is

0.00000003 cm!

Unit 3: Chemistry. Introduction to Atoms.

LET’S WATCH THE TED ED VIDEO! https://www.youtube.com/watch?v=yQP4UJhNn0I

Unit 3: Chemistry. Introduction to Atoms.

What is inside an atom?

Electrons: are negatively charged particles found

in electron clouds outside the nucleus.

The Nucleus: is the small, dense,

positively charged center of the atom. It contains most of the

atom’s mass.

The diameter of the nucleus is 1/100,000 the diameter of

the atom.

Protons: are positively charged particles in the

nucleus if the atom.

Neutrons: are particles in the nucleus of an

atom that have no charge.

Unit 3: Chemistry. Introduction to Atoms.

Atomic mass unit (amu): the SI unit used to express the masses of particles in

atoms

Neutron

Charge: none

Mass: 1 amu

Location: nucleus

Electron

Charge: negative

Mass: almost zero

Location: electron clouds

Proton

Charge: positive

Mass: 1 amu

Location: nucleus

Unit 3: Chemistry. Introduction to Atoms.

Fun Fact: If it were possible to have a nucleus the volume of an average grape, that nucleus

would have a mass greater than 9 MILLION TONS!

Unit 3: Chemistry. Introduction to Atoms.

The atom is neutral when there are equal number protons and electrons.

If the number of protons

and electrons are not equal, the atoms

becomes a charged particle called an ion.

Unit 3: Chemistry. Introduction to Atoms.

Stop and think… 1)What particles form the

nucleus? 2)Explain why atoms are

neutral.

Atomic number: the number of protons in the nucleus.

This # determines what type of element it is!

Unit 3: Chemistry. Introduction to Atoms.

Atomic mass: the sum of the protons and neutrons in an

atom