Chapter 2: Atoms, Molecules, and Ions

Atom

Atom

Mostly empty space and consist of subatomic particles.

Proton

Subatomic particle with a positive charge found in the nucleus of an atom.

Neutron

Subatomic particle with a neutral charge found in the nucleus of an atom.

Electron

Subatomic particle with a negative charge that orbits the nucleus of an atom.

Atomic Number

The number of protons in the nucleus of an atom, also indicating the number of electrons.

Isotope

Atoms of the same element with different masses due to varying numbers of neutrons.

Atomic Mass Unit (amu)

Unit used to express the mass of atoms on an atomic scale;

1 amu = 1.66054 × 10^24- g

Atomic Weight

An average mass is found using all isotopes of an element weighted by their relative abundances.

Atomic Weight Formula

\sum [(isotope mass)x(fractional natural abundance)] for ALL isotopes.

Periodic Table

Systematic arrangement of elements based on atomic number.

Periods

The horizontal rows that represent the number of electron shells an element's atoms have; there 7 rows in the periodic table.

Groups

The columns that contain elements with similar chemical properties due to the same number of electrons in their outer shell.

Group 1A

Contains Alkali metals.

Group 2A

Contains Alkaline earth metals.

Sections 3-12

The transition metals of the periodic table.

Group 6A

Contains Chalcogens.

Group 7A

Contains Halogens.

Group 8A

Contains Noble gases.

Metals

Located on the left side of the periodic table; properties include shiny luster, conducting heat and electricity, and solid (except Hg).

Nonmetals

Elements on the right side of the periodic table that lack metallic properties; mostly gases, but can be solid or liquid.

Metalloids

Elements with properties intermediate between metals and nonmetals, located along a "stair step" on the periodic table.

Molecular Compounds

Formed by sharing electrons between atoms to create covalent bonds; consist of molecules made up of nonmetals.

Ionic Compound

Compound formed by the attraction between oppositely charged ions, typically between a metal and a nonmetal.

Diatomic Molecules

Molecules composed of two atoms chemically bonded together; examples include Hydrogen (H₂), Oxygen (O₂), Nitrogen (N₂), and Chlorine (Cl₂).

Empirical Formulas

Show the simplest whole-number ratio of atoms in a compound.

Molecular Formulas

Shows the exact number of atoms of each element in a compound.

Ion

A charged atom.

Cation

Formed when at least one electron is lost.

Anion

Formed when at least one electron is gained.

Polyatomic ions

Many atoms grouped together.M

Mono-

1

Di-

2

Tri-

3

Tetra-

4

Penta-

5

Hexa-

6

Hepta-

7

Octa-

8

Nona-

9

Deca-

10