Chapter 3

Alkaline Earth Metals

An element from Group 2A of the periodic table

Anion

A negatively charged ion

Alkali metals

An element (except H) from Group 1A of the periodic table

Atom

The smallest particle of an element that can enter into a chemical reaction

Cation

A shorthand method for showing the composition of a compound, using symbols of the elements

Elements

A basic building block of matter that cannot be broken down into simpler substnaces by ordinary chemical changes; in 1994, there were 111 known elements

Law of definite composition

A compound always contains two or more elements in a definite proportion by massCom

Compound

A distinct substance composed of two or more elements combines in a definite proportion by mass

Ion

A positively or negatively charged atom or group of atoms

Diatomic molecules

The molecules of elements that always contain two atoms. Seven elements occur as diatomic molecules: H2, N2, O2, F2, Cl2, Br2 and I2

Halogens

Group 7A of the periodic table; consists of the elements flourine, chlorine, bromine, iodine, and astatine

Molecule

The smallest uncharged individual unit of a cmpound formed by the union of two or more atoms

Subscript

Number that appears partially below the line and to the right of a symbol of an element

Natural law

A statement summarizing general observations regarding nature

Metalloid

An element having properties that are intermediate between those of metals and nonmetals; these elements are useful in electronics

Nonmetal

An element that has properties the opposite of metals: lack of luster, relatively low melting point and density, and generally poor conduction of heat and electricity. _____ may or may not be solid at room temperature; many gases. They are located mainly in the upper right-hand corner of the periodic table

law of multiple proportions

Atoms of two or more elements may combine in different ratios to produce more than one compound

Nobel gases

A family of elements in the periodic table- helium, neon, argon, krypton,xenon, and radon- that contains a particularly stable electron structure

Metal

An element that is solid at room temperatire and whose properties include luster, ductility, malleability, and good conductivity of heat and electricity; metals tend to lose their valence electrons and become positive ionsSyb

Symbol

In chemistry, an abbreviation for the name of an element

Jons jakob Berzelius

A Swedish scientist who introduced the modern system of chemical symbols in 1813. he represented the elements using one ore two letters from their Latin names.