Other Things that are Good to Know

The Law of Definite Proportions

a specific chemical compound always contains the exact same elements in the same fixed proportions by mass, regardless of the source or how the compound was prepared

The Law of Multiple Proportions

when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of simple whole numbers

Octet rule

atoms tend to gain, lose, or share electrons until they have a full outer shell of eight valence electrons

Metals, nonmetals, and metalloids

metals: shiny, conductive, malleable

nonmetals: dull, insulative, brittle

metalloids: properties of both

predictable periodic property

A predictable periodic property (periodic trend) is a characteristic of elements that repeats in a regular, rhythmic pattern (periodicity) as you move across or down the periodic table.

How is the periodic table arranged to display chemical properties?

The periodic table is arranged by increasing atomic number (number of protons). Also, it is organized by groups and periods.

What physical properties can be predicted using the periodic table?

Density, atomic mass, state of matter, melting and boiling points, malleability and ductility.

Coulomb’s Law

The attractive force between charged particles increases with greater particle charge and decreases with larger distance between them.

Atomic radius

The distance from the nucleus to the outermost electron shell of an atom. It typically increases down a group and decreases across a period due to changes in electron shielding and effective nuclear charge.

Ionization energy

The energy required to remove an electron from an atom or ion. It generally increases across a period and decreases down a group due to effective nuclear charge changes.

Electronegativity

is the measure of an atom's ability to attract and hold electrons in a bond. It typically increases across a period and decreases down a group.