Atoms and the Periodic Table

A comprehensive vocabulary review of atomic structure, subatomic particles, isotopes, and groups and trends in the periodic table.

Element

Matter that is composed of one type of atom

Chemical symbol

Scientific shorthand that is made up of either one letter or a pair of letters

Atom

Smallest piece of matter that still has the properties of the element

Proton

The part of an atom with a positive charge

Neutron

The part of an atom with neutral or no charge

Electron

The part of an atom with a negative charge

Nucleus

Located in the center of an atom and consists of protons and neutrons

Electrons (surrounding structure)

These surround the nucleus

Electron cloud

Model of the atom that shows electrons traveling in specific energy levels around a nucleus

Valence electrons

Electrons that are farthest from the nucleus that are involved in bonding

Quarks

Smaller particles that make up protons and neutrons

Atomic mass

Composed mostly of protons and neutrons in the nucleus

Atomic number

The number of protons in an atom; this identifies the element

Number of neutrons

Found by the calculation: $\text{Mass number} - \text{atomic number}$

Isotope

Atoms of the same element that have different number of neutrons

Average atomic mass

Weighted average mass of an element's isotopes

Radioactive decay

When the nuclei of unstable isotopes release fast-moving particles and energy

Periodic table

Table where elements are organized by increasing atomic number

Groups

Vertical columns of elements

Elements in the same group

Elements in the same group have the same number of valence electrons

Periods

Horizontal rows on the periodic table

Elements in the same period

Elements in the same period on the periodic table have the same number of electron shells

Electron dot diagram

This shows how many valence electrons an element has, using its chemical symbol and dots

Conductivity of metals

Metals are good conductors of heat and electricity

State of metals at room temperature

Except for mercury, metals are solid at room temperature

Malleable

Metals that are able to be hammered into thin sheets

Ductile

Metals that are able to be stretched into long wires

Alloy

A mixture of metals that combines the best properties of two or more metals into a single substance

Alkali metals

Elements in group 1 that are the most reactive

Alkaline earth metals

Elements in group 2 that are shiny, ductile and malleable

Transition metals

Elements in groups 3-12; most familiar metals are found here because they occur in nature uncombined

Inner transition metals

Elements listed below the periodic table; also called rare earth elements

Nonmetals

Elements that are usually gases or brittle solids at room temperature

Conductivity of nonmetals

Nonmetals are poor conductors of heat and electricity

Halogens

Elements in group 17 that form salts when combined with metals

Noble gases

Elements in group 18 that exist as isolated atoms; they do not ordinarily form compounds

Metalloids

Elements that make up the stair step on the table; they have metallic and non-metallic properties