Atoms-
Basic Units of Matter

What is the current atomic model?

Inside the Atom

Parts of Atoms- Protons, Neutrons, and Electrons

The Size of Atoms

An atom's protons and neutrons are packed tightly together

Protons and Neutrons have about the same mass

Neutron- particle that contains no charge

Proton- positively charged particle in the nucleus

The first atomic-force microscope was invented in the 1980's

The atom is mostly full of empty space

Nucleus- is located in the middle of the atom. contains most of the atom's mass

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Matter is anything that has mass and takes up space

Atom's are very small particles that makes up all matter

Electron- negatively charged particle that moves in the space around the nucleus

Is there historical evidence of atoms

Democritus and the Atom

The Law of Conservation of Mass

Dalton's Atomic Model

Each time new evidence becomes available, the model of atomic structure becomes clearer and more accurate

c. 460-370 B.C.

Believed that Atoms were indivisible

He thought that atoms were small solid spheres with no holes and no empty space inside

He wanted to be able to cut open an atom

Antoine Lavoisier (1743-1797)

Lavoisier measured mercury into a sealed container and and heated it to see if something different would happen

Something changed instead of being red it turned into a slivery liquid. This happened because of Oxygen

He found that the total mass of the starting materials was always the same as the total mass of the products

The law of conservational mass states that the mass of the products always is the same as the mass of the starting materials

The Law of Definite Proportions

1779 J.L. Proust analyzed a variety of pure compounds to determine their composition

Pure compounds always contain the same elements in the same proportion by mass

John Dalton (1766-1844)

He made symbols for the known elements

He had an atomic theory that had five principles

  1. All matter is made up of atoms
  1. Atoms are neither created nor destroyed in chemical reactions
  1. Atoms of different elements combine in whole-number ratios
  1. Each element is made of a different kind of atom.
  1. The atoms of different elements have different masses and properties