Families of Elements - Key terms





ACTINIDES:

Those transition metalsthat fill the 5 f orbital. Because actinium—which does not fill the 5 f orbital—exhibits characteristics similar to those of the actinides, it is usually considered part of the actinides family.

ALKALI METALS:

All members, excepthydrogen, of Group 1 on the periodic table of elements, with valence electron configurations of n s 1 .

ALKALINE EARTH METALS:

Group 2 on the periodic table of elements, with valence electron configurations of n s 2 .

ELECTRON CLOUD:

A term used to describe the pattern formed by orbitals.

FAMILIES OF ELEMENTS:

Related elements, including the noble gases, halogens, alkali metals, alkaline earth metals, transition metals, lanthanides, and actinides. In addition, metals, nonmetals, and metalloids form loosely defined families. Other family designations—such as carbon family—are sometimes used.

GROUND STATE:

A term describing the state of an atom at its ordinary energy level.

GROUPS:

Columns on the periodic table of elements. These are ordered according to the numbers of valence electrons in the outer shells of the atoms for the elements represented.

HALOGENS:

Group 7 of the periodic table of elements, with valence electron configurations of n s 2 n p 5 .

ION:

An atom or atoms that has lost or gained one or more electrons, and thus has a net electric charge.

LANTHANIDES:

The transition metalsthat fill the 4 f orbital. Because lanthanum—which does not fill the 4 f orbital—exhibits characteristics similar to those of the lanthanides, it is usually considered part of the lanthanide family.

MAIN-GROUP ELEMENTS:

The 44 elements in Groups 1 through 8 on the periodic table of elements, for which the number of valence electrons equals the group number. (The only exception is helium.) The main-group elements, also called representative elements, include the families of alkali metals, alkali earth metals, halogens, and noble gases, as well as other metals, nonmetals, and metalloids.

METALLOIDS:

Elements which exhibit characteristics of both metals and nonmetals. Metalloids are all solids, but are not lustrous or shiny, and they conduct heat and electricity moderately well. The six metalloids occupy a diagonal region between the metals and nonmetals on the right side of the periodic table. Sometimes astatine is included with the metalloids, but in this book it is treated within the context of the halogens family.

METALS:

A collection of 87 elements that includes numerous families—the alkali metals, alkaline earth metals, transition metals, lanthanides, and actinides, as well as seven elements in groups 3 through5. Metals, which occupy the left, center, and part of the right-hand side of the periodic table, are lustrous or shiny in appearance, and malleable, meaning that they can be molded into different shapes without breaking. They are excellent conductors of heat and electricity, and tend to form positive ions by losing electrons.

NOBLE GASES:

Group 8 of the periodic table of elements, all of whom (with the exception of helium) have valence electron configurations of n s 2 np 6 .

NONMETALS:

Elements that have a dull appearance; are not malleable; are poor conductors of heat and electricity; and tend to gain electrons to form negative ions. They are thus the opposite of metalsin most regards, as befits their name. Aside from hydrogen, the other 18 nonmetals occupy the upper right-hand side of the periodic table, and include the noble gases, halogens, and seven elements in groups 3 through 6.

ORBITAL:

A pattern of probabilities regarding the position of an electron for anatom in a particular energy state. The higher the principal energy level, the more complex the pattern of orbitals. The four types of orbital patterns are designated as s, p, d, and f —each of which is more complex than the one before.

PERIODIC TABLE OF ELEMENTS:

A chart that shows the elements arranged in order of atomic number, along with chemical symbol and the average atomic mass (in atomic mass units) for that particular element.

PERIODS:

Rows of the periodic table of elements. These represent successive energy levels in the atoms of the elementsinvolved.

PRINCIPAL ENERGY LEVEL:

A value indicating the distance that an electron may move away from the nucleus of anatom. This is designated by a whole-number integer, beginning with 1 and moving upward. The higher the principal energy level, the greater the energy in the atom, and the more complex the pattern of orbitals.

REPRESENTATIVE ELEMENTS:

See main-group elements.

TRANSITION METALS:

A group of 40 elements, which are not assigned a group number in the North American version of the periodic table. These are the only elements that fill the d orbitals.

VALENCE ELECTRONS:

Electrons that occupy the highest energy levels in anatom. These are the electrons involved in chemical bonding.