Vocabulary
Atomic Structure
Metals
Elements that are lustrous, shiny, hard, malleable, ductile, and lose electrons easily.
Metals conduct heat and electricity well. Metals are found to the left of the Periodic
Table.
Malleable
Capable of being stretched, hammered, shaped, or bent into different shapes
Nonmetals
Elements that are soft, brittle, and dull. They are poor conductors of heat and
electricity. Nonmetals are found in the upper right corner of the Periodic Table.
Chemical
property
A characteristic that describes the atomic or elemental composition of a substance. It
can be observed during a chemical reaction.
Metalloid
An element that can possess properties of both metals and nonmetals.
Element
A substance that cannot be broken down into smaller components by chemical means.
There are 90 naturally occurring elements and a total of about 112 known elements.
Periodic Table of A table that organizes the elements according to their physical and chemical
the Elements
properties.
Atomic Number
The number of protons found in the nucleus of an element’s atom.
Atomic Mass
The mass of an atom. The atomic mass is equal to the sum of the number of protons
and neutrons in the nucleus of an element’s atom.
Electron
A subatomic particle with a negative charge that is found in a cloud around the
nucleus of an atom. Electrons have very little mass compared to the mass of a proton
or a neutron.
Proton
A subatomic particle with a positive charge found in the nucleus of an atom. The mass
of a proton is equal to the mass of a neutron and has a mass of 1.
Neutron
A subatomic particle with no (neutral) charge found in the nucleus of an atom. The
mass of a neutron is equal to the mass of a proton and has a mass of 1.
Atom
The smallest particle of an element that still has all the properties of that element.
Nucleus
The center mass of an atom. It contains protons and neutrons.
Matter
Anything that occupies space and has mass.
Physical
property
A property of a substance that can be observed without changing the substance’s
identity. The characteristics of a substance that describe its shape, size, form, or state
of matter.
Ion
An atom whose number of electrons does not equal its number of protons.
Isotopes
Elements that have the same number of protons but a different number of neutrons.
Period
A horizontal row in the Periodic Table. Elements in a period all have the same number
of electron energy levels.
Group
A vertical column in the Periodic Table, also known as a family. Elements in a group all
have the same number of valence electrons.
Valence
electrons
The electrons found in the outermost energy level of an atom. Valence electrons
determine the atom’s chemical properties.
Electron energy
levels
Within the electron cloud that surrounds the nucleus, electrons can be found in
specific energy levels. The first level holds at most 2 electrons, the second level can
hold up to 8 electrons, the third level holds up to 18 electrons, the fourth level holds
up to 32 electrons. There are a total of seven energy levels in the current known
elements.
Subatomic
Particles
Particles that make up an atom. Protons, neutrons, and electrons are subatomic
particles.