C.6A: Atomic Theory

C.6A: Atomic Theory

Picture Vocabulary

© 2012 Rice University - All Rights Reserved

John Dalton

A chemist in the early 1800s who proposed the first theory to relate chemical changes to

events at the atomic level © 2012 Rice University - All Rights Reserved

J.J. Thomson

A scientist in the late 1800s who discovered electrons through his explorations on the

properties of cathode rays


Ernest Rutherford

A scientist who first described the atom as having a central positive nucleus surrounded

by negative orbiting electrons


Niels Bohr

A scientist who developed the modern model of an atom which expanded on Rutherford’s description by explaining that electrons travel

only in certain successively larger orbits © 2012 Rice University - All Rights Reserved

Atomic Theory

The theory of the nature of matter which states that all matter is composed of tiny

indivisible particles known as atoms


Postulate

Statements that are assumed to be true without proof


Dalton’s Postulates

Four postulates that were used to explain earlier observations of the behavior of matter:

A) All matter is composed of small, indivisible particles called atoms B) All atoms of a given element are identical in mass and properties C) Compounds are formed by a combination of two or more atoms in definite arrangements in the ratio of small whole numbers D) Atoms are not created, destroyed or converted into other kinds of atoms during chemical reactions, they are simply rearranged into new compounds

Fire is a chemical change that can rearrange, but not destroy atoms.


Particle (Physics)

A particle made up of two protons and two neutrons that is emitted from a radioactive

source


Electron Orbital

The specific regions around the nucleus of an atom in which electrons travel


Nuclear Atom

A conceptual model of the atom developed by Ernest Rutherford in which a small

positively charged nucleus is surrounded by orbiting negatively charged electrons


Nucleus

The tiny, very dense, positively charged region in the center of an atom; made up of

protons and neutrons


Electrical Charge

A form of charge, designated negative, positive, or neutral (without charge) that is found on the

subatomic particles that make up all atoms


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C.6A: Atomic Theory