Science Atomic Theory

Democritus

Stated the idea that all matter is made of tiny, indestructible, things called atoms

Ernest Ruthorford

Stated the idea that most of an atoms mass is in its tiny nucleus, and the rest is mainly empty space

John Dalton

Revolutionized our knowlege of atoms with his four part theory

Dalton’s Four Part Theory

1. All matter is composed of atoms. 2. Atoms of a given element are identical in mass and properties. 3. Atoms cannot be subdivided, created, or destroyed. 4. Atoms of different elements combine or be rearranged to form chemical reactions.

Dimitri Mendeleev

Came up with the original periodic table based on atomic mass rather than atomic numbers like the one today

JJ Thomson

Discovered that electrons make up atoms, made the plum pudding diagram

Plum Pudding Model

Chemistry

The study of matter and its interactions with other matter

Atoms

The basic units of matter, consisting of a nucleus surrounded by electrons. They determine the chemical properties of elements.

Elements

Pure structures that cannot be broken down further by chemical means

Protons

These make up an atoms nucleus and have a positive charge

Neutrons

These make up an atoms nucleus and have a neutral charge

Electrons

Subatomic particles that have a negative charge and orbit the nucleus of an atom.

Atomic Number

The number of protons (and electrons) in an atom's nucleus, which determines the chemical element and its properties. These organize our periodic table

Atomic Mass

The mass of an atoms nucleus, determined by the # of protons + neutrons, this organized Mendeleev’s periodic table

Electron Clouds

The area where electrons orbit the nucleus of an atom

Orbital

A region in an atom where there is a high probability of finding electrons.

Isotopes

Atoms of the same element with different numbers of protons (resulting in different atomic mass)

Average Atomic Mass

What you get when you average the masses of all isotopes of an element

amu

(atomic mass unit), standard unit of mass used to measure atomic weight

Atomic Number

Avg. Mass Number