|The "size" of an atom. Across a single period of the Periodic Table, the atomic radius generally decreases as the atomic number increases.
|A set of characteristics that are used to identify a substance based upon its chemical activity.
|The ability of a substance to conduct electricity (a flow of electrons).
|A solid with a regular geometric pattern. All true solids have a crystalline structure.
|A measure of the ability of an atom to attract the electrons that form a bond between it and another atom. Electronegativity is defined on an arbitrary scale relative to fluorine which is assigned a value of 4.0.
|A family of elements shown on the Periodic Table as a column. For example, the elements F, Cl, Br, I, and At are all members of Group 17.
|The amount of energy required to remove the most loosely bound electron from an atom in the gaseous phase.
|Capable of being molded, hammered, or beaten into sheets.
|Elements are located to the left of the "black staircase" of the Periodic Table. Properties of metals: Metal atoms have relatively low ionization energies and low electronegativities. Metal atoms tend to lose electrons, forming positive ions when combining with other elements. Metals are usually good conductors of heat and electricity. Metals are usually solids at room temperature . Metals are usually lustrous (shiny), malleable (can be hammered, rolled or pressed into shape), and ductile (can be drawn out or hammered thin).
|An element that has properties of both metals and nonmetals. The metalloids are found adjacent to the dark staircase in the Periodic Table of the Elements.
|A gas in Group 18 of the Periodic Table.
|Elements located to the right of the "black staircase" on the Periodic Table. Properties of nonmetals: Nonmetal atoms have high ionization energies and high electronegativities. Nonmetals tend to gain electrons when in combination with metals, or to share electrons when in combination with other elements. Nonmetal solids are usually dull and brittle, and they are poor conductors of heat and electricity.
|One of the horizontal rows of the Periodic Table of the Elements.
|Development of Periodic Table
|The Periodic Table of the Elements has passed through many stages of development. The atomic number is the basis of the arrangement in the present form of the Periodic Table. The properties of the elements depend on the structure of the atom and vary with the atomic number in a systematic way (the Periodic Law).
|Properties of Elements of Periodic Table
|The horizontal rows of the Periodic Table are called periods. The properties of elements change systematically across a period. The vertical columns of the Periodic Table are called groups or families. The elements of a group exhibit similar or related properties.
|An electron in the outermost principal energy level of an atom.