Unit 3-Atoms/Atomic Structure/Subatomic Particles

Atom

The smallest part of an element

Molecule

The smallest particle of a substance that is made of at least two atoms

Diatomic molecule

A molecule composed with only two atoms

Polyatomic molecule

A molecule composed of three or more atoms

BrINClHOF

An acronym used to remember the seven elements that are always diatomic when found free in nature.

Dalton’s Atomic Theory

Named after Dalton, introduced his theory in the 1800s, composed of 4 postulates or statements.

Postulate 1

All elements are composed of submicroscopic indivisible particles called atoms.

Postulate 2

Atoms of the same element are identical, the atoms of any one element are different from those of any other element.

Postulate 3. A)

Atom of different elements can physically mix together. (We call those Mixtures)

Postulate 3. B)

Atoms of different elements can chemically combine with one another in simple whole number ratios to form compounds.

Postulate 4

Chemical reactions occur when atoms are (1) separated, (2) joined, (3) rearranged. However l, atoms of one element are never changed into atoms of another element as the result of a chemical reaction.

Bhor’s Atomic Theory

Named after Bhor, introduced his theory in the 1900s, states that electrons move around the nucleus of an atom like the planets move around the sun.

Rutherford’s Atomic Theory

The good foil experiment concluded: most of the atom must consist of _____ without the _____. The nucleus must occupy a very small portion of the atom.

Nucleus

The dense positively charged center of the atom

AMU

Atomic Mass Unit: 1/12th of 1 carbon atom

Proton

Positively charged, in the nucleus, mass of 1 AMU

Neutron

Uncharged, in the nucleus, mass of 1 AMU

Isotope

Atoms of the same element but with a different number of neutrons

Atomic # =

the # of protons

Atomic mass =

Sum of protons + neutrons

Common carbon’s Atomic Mass

12 AMUs

Common name of ^12 C *6

Carbon-12

Use for Carbon-14

Carbon dating

Most common Hydrogen isotope

Protium, 1 proton, 1 neutron, 1 AMU

Deuterium

0 protons, 1 neutrons, 2 AMUS