Chemistry Chapter 4 Definitions

Element Symbol

a letter code for an element that is usually one to two letters long

Law of Constant Composition

a given compound always contains elements in exactly the same proportion by mass

Dalton's Atomic Theory

a theory established by John Dalton in the early 1800s, used to explain the nature of materials

Atom

the smallest component of an element having the chemical properties of the element

Compound

a substance made of two or more different elements joined together in a specific way

Chemical Formula

a representation of a molecule in which the symbols for the elements are used to indicate the types of atoms present, and subscripts are used to show the relative numbers of atoms

Electron

negatively charged subatomic particles

Nucleus

the relatively small and dense center of positive charge in an atom

Proton

a positively charged subatomic particle located in the atomic nucleus

Neutron

a subatomic particle in the atomic nucleus with no charge

Isotope

atoms with the same number of protons but different numbers of neutrons

Atomic Number

the number of protons in the nucleus of a given atom

Mass Number

the total number of protons and neutrons in the nucleus of a given atom

Periodic Table

a chart showing all the elements arranged in columns in such a way that all the elements in a given column exhibit similar chemical properties

Group

vertical columns of elements on the periodic table

Alkali Metal

group 1A metals

Alkaline Earth Metals

group 2A metals

Halogen

group 7A metals

Noble Gas

group 8A metals

Transition Metal

several series of elements in which inner orbitals ( or orbitals) are being filled

Metal

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Non Metal

an element that does not exhibit metallic characteristics; chemically, a typical nonmetal accepts electrons from a metal

Metalloid

elements that have both metallic and nonmetallic properties

Law of Conservation of Mass

mass is neither created nor destroyed

Ion

an atom or group of atoms that has a positive or negative charge

Cation

a positively charged ion

Anion

a negatively charged ion

Ionic Compound

a compound that results when a metal reacts with a nonmetal to form cations and anion