7 September 20157 September 2015Name the following by using what you

have already memorized!1)Li3PO4

2)NaOH3)CaSO4

4)KNO3

Pick up a BellWork sheet, to start fresh!

Bellwork 9/10/15Bellwork 9/10/15• Name three people that

contributed to the history of the atom and list at least two facts about each person.

Think about what you think an atom looks like & how to describe its size; write his in your notes.

Today we are going Today we are going to…to…

• Explore the size of an atom.• Discover the historical development of the atom.

Ancient GreeksAncient Greeks

• Aristotle believed that there are only four elements in the universe.

• 400 B.C.E.

• Proposed that matter was composed of tiny indivisible particles

• Based on thought not experimentation

• Coined the Greek term “Atomos” meaning--indivisible

DemocritusDemocritus

• 500BCE to 1720

• Mixture of science and mysticism.

• Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.

AlchemistsAlchemists

DaltonDalton• Noticed that all compounds had something in common.

• No matter how large or small the sample was.

Dalton’s TheoryDalton’s Theory• All elements are

composed of atoms.

Dalton’s TheoryDalton’s Theory• All atoms of

the same element have the same mass, and atoms of different elements have different masses.

Dalton’s TheoryDalton’s Theory

• Compounds contain atoms of more than one element.

Dalton’s TheoryDalton’s Theory• In a particular

compound, atoms of different elements combine in the same way.

Dalton’s ModelDalton’s Model• Dalton's

model of the atom, a solid sphere was an early model of the atom.

Daltons Atomic TheoryDaltons Atomic TheoryAll matter is made of atoms

A chemical reaction is a rearrangement of atoms

Postulate 1

All atoms of an element are identical in mass and property

Compounds are formed of two or more types of elements

Postulate 2

Postulate 3

Postulate 4

Postulate 5

Atoms are indivisible and indestructible

Dalton’s Theory ErrorsDalton’s Theory Errors• Mostly holds up today with only a few errors.

• Atoms are made of protons, neutrons, electrons

Postulate 2 • Atoms are indivisible and

indestructible

Dalton’s Theory ErrorsDalton’s Theory Errors

• We now know of the existence of isotopes. Atoms of the same element that have different masses

• Other than that…everything else is correct.

• All atoms of an element are identical in mass and property

Postulate 3

Thomson’s ExperimentThomson’s Experiment

Thomson’s ModelThomson’s Model

Thomson’s ModelThomson’s Model

ThomsonThomson• Provided the first evidence that atoms are made of even smaller particles.

• From his experiment he discovered that there were negatively charged particles in the atom, which he called electrons

• He designed a model of the atom, called the plum pudding model.

• This atomic model: a positively charged jelly-like atom with “corpuscles” of negative charges called electrons

Rutherford’s ExperimentRutherford’s Experiment

• Experiment Animation

Gold Foil ExperimentGold Foil Experiment

Rutherford’s ModelRutherford’s Model

• All of an atom’s positive charge is concentrated in its nucleus.

Rutherford ModelRutherford Model

Nuclear Modeldense, positive nucleus surrounded by negative electrons

Bohr ModelBohr Model• Niels Bohr (Danish Physicist)

• Electrons move around the nucleus of the atom the same way that planets move around the sun.

Foundation of the Foundation of the Bohr ModelBohr Model

Each electron has a specific amount of energy

If an atom gains or loses energy, the energy of an electron can change.

The possible energies that electrons in an atom can have are called ENERGY LEVELS

An electron in an atom can move from one energy level to another when the atom gains or loses energy

Bohr ModelBohr Model Planetary System Model

Positively Charge Nucleus

Electrons orbiting the nucleus in fixed energy levels

“Excited” electrons jump energy levels