- Group:
The vertical columns on the periodic table. - Periods:
The horizontal rows on the periodic table. - Element:
A substance that can not be decomposed into simpler substances by chemical means. - Compound:
A substance of two or more elements in fixed proportions. Compounds can be decomposed into their constituent elements. - Atomic Number:
Integral number of protons in the nucleus; defines the identity of element. - Atomic Mass:
One twelfth of a mass of an atom of the carbon-12 isotope; a unit used for stating atomic and formula weights; also called dalton. - Atom:
the defining structure of an element , which cannot be broken by any chemical means. A typical atom consists of a nucleus of protons and neutrons with electrons orbiting this nucleus.- Ion:
An atom or a group of atoms that carries an electric charge. - Valence Electron:
Outermost electrons of atoms; usually those involved in bonding. - Metal:
An element below and to the left of the stepwise division (metalloids) in the upper right corner of the periodic table; about 80% of the known elements are metals. - Nonmetal:
An element or substance that is not a metal. - Metalloids:
Elements with properties intermediate between metals and nonmetals. - Noble Gas:
Elements of the periodic Group 0; also called rare gases; formerly called inert gases. - Alkali Metal:
Metals of Group IA (Na, K, Rb). - Alkaline Earth Metal:
Group IIA metals. - Halogen:
Group VIIA elements: F, Cl, Br, I. - Cation:
A positive ion; an atom or group of atoms that has lost one or more electrons. - Anion:
A negative ion; an atom or group of atoms that has gained one or more electrons. - Electron Affinity:
The amount of energy absorbed in the process in which an electron is added to a neutral isolated gaseous atom to form a gaseous ion with a 1- charge; has a negative value if energy is released. - A measure of the relative tendency of an atom to attract electrons to itself when chemically combined with another atom. As you move across the periodic table to the right, electronegativity in the elements increase. As you move down a group in the periodic table, the electronegativity decreases.
- Ionization Energy (explain the trend):
The minimum amount of energy required to remove the most loosely held electron of an isolated gaseous atom or ion. Going across the periodic table to the right, ionization energy increases, and going down a group, ionization energy decreases. - Atomic Radii (explain the trend):
Radius of an atom. Going across the periodic table to the right, the atomic radius decreases and, going down a group, the atomic radius increases. - Density:
Mass per unit Volume: D=MV - Melting Point:
The temperature at which liquid and solid coexist in equilibrium; also the freezing point. - Reactivity:
- the defining structure of an element , which cannot be broken by any chemical means. A typical atom consists of a nucleus of protons and neutrons with electrons orbiting this nucleus.