GLOSSARY Actinides
The actinides comprise elements 89 through 103. They, along with the actinides, are often called the f-elements because they have valence electrons in the f shell. Alkali Metals
The alkali metals make up the first column (group) of the periodic table, and comprise Li through Fr. Alkaline Earth Metals
The alkaline earth metals make up the second column (group) of the periodic table, from Be through Ra. Atomic Number
The atomic number is the number of protons in an atomic nucleus. Atomic Orbital
Atomic orbitals are regions of space around the nucleus of an atom where an electron is most likely to be found. Atomic Radius
The atomic radius is the total distance from an atom's nucleus to the outermost electron orbital. Atomic Weight
The atomic weight is the average mass of an atom of an element. Chemical Symbol
A chemical symbol is a notation of one or two letters representing a chemical element. Conductor
A material that conducts heat or electricity, which means electrons can easily flow through the object. Diatomic
A complex consisting of two atoms. The D-block
The d-block is the section of elements on the periodic table in groups 3 – 12. Electron Affinity
Electron affinity is the amount of energy absorbed when an electron is added to an atom. Electronegativity
Electronegativity is a measure of the attraction an atom has for electrons. Element
An element is a substance composed of atoms with identical atomic number. Exothermic
Exothermic is the term used to describe a reaction that releases heat. The F-block
The f-block is the section of elements below the main section of the periodic table consisting of the lanthanide and actinide elements. Family
A family is also called a group. It is a column of elements in the periodic table that all have similar properties. Flame Test
A flame test is a test for detecting the presence of certain metals by determining the color they emit when put in a flame. Group
A group is also called a family. It is a column of elements in the periodic table that all have similar properties. Halogens
The halogen elements are a subset of the nonmetals. They comprise group 17 of the periodic table, from F through At. Ionization Energy
The ionization energy is the energy needed to remove an electron from an atom. Lanthanides
The lanthanides comprise elements 57 through 71. Along with the actinides they are often called the f-elements because they have valence electrons in the f shell. Main-Group Elements
Groups 1-2 and 13-18 are called the main-group elements. Malleability
Malleability means an object is capable of being hammered into sheets or shapes. Metalloids
Metalloids are also called semi-metals. They are the elements B, Si, Ge, As, Sb, Te, and Po. Metals
A metal is a substance that conducts heat and electricity, is shiny, and can be hammered into sheets or drawn into a wire. Noble Gases
The noble gases comprise group 18. They are generally very stable, colorless, and odorless. Non-Metals
The term non-metals is used to classify the elements H, C, N, P, O, S, and Se. Oxidation State
The oxidation state is the charge associated with an atom. Oxide
An oxide is a compound composed of a metal and oxygen. The P-block
The p-block is the section of the periodic table composed of the last six groups or columns. Period
A period is a horizontal row of the periodic table. Periodic Law
The periodic law is the principle that the properties or characteristics of the elements recur periodically as their atomic numbers increase. The S-block
The s-block is the section of elements on the periodic table composed of the first two groups or columns. Transition Metals
The transition elements are metals that have a partially filled d subshell and comprise groups 3 through 12 and the lanthanides and actinides. Valence Electrons
Valence electrons are the electrons of an atom that are highest in energy and in the outermost orbitals.