Transition Metals - 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.

ALLOY:

A mixture containing more than one metal.

ELECTROLYSIS:

The use of an electric current to cause a chemical reaction.

ELECTRON CLOUD:

A term used to describe the pattern formed by orbitals.

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.

INNER TRANSITION METALS:

The lanthanides and actinides, both of which fill the f orbitals. For this reason, they are usually treated separately.

ION:

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

ISOTOPES:

Atoms that have an equal number of protons, and hence are of the same element, but differ in their number of neutrons. This results in a difference ofmass. Isotopes may be either stable or unstable. The latter type, known as radioisotopes, are radioactive.

IUPAC SYSTEM:

A version of the periodic table of elements, authorized by the International Union of Pure and Applied Chemistry (IUPAC), which numbers all groups on the table from 1-18. Thus in the IUPAC system, in use primarily outside of North America, both the representative or main-group elements and the transition metals are numbered.

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.

NORTH AMERICAN SYSTEM:

A version of the periodic table of elements that only numbers groups of elements in which the number of valence electrons equals the group number. Hence the transition metalsare usually not numbered in this system. Some North American charts, however, do provide group numbers for transition metals by including an "A" after the groupnumbers for representative or main-group elements, and "B" after those of transition metals.

ORBITAL:

A pattern of probabilities indicating the regions that may be occupied by an electron. The higher the principal energy level, the more complex the pattern of orbitals.

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. Elements are arranged in groups or columns, as well as in rows or periods, according to specific aspects of their valence electron configurations.

PERIODS:

Rows on the periodic table of elements. These represent successive principal energy levels for the valence electrons in the atoms of the elements involved. Elements in the transition metal family occupy periods 4, 5, 6, or 7.

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. Elements in the transition metal family have principal energy levels of 4, 5,6, or 7.

RADIOACTIVITY:

A term describing a phenomenon whereby certain isotopes known as radioisotopes are subject to a form of decay brought about by the emission of high-energy particles. "Decay" does not mean that the isotope "rots"; rather, it decays to form another isotope until eventually (though this may take a long time), it becomes stable.

REACTIVITY:

The tendency for bonds between atoms or molecules to be made or broken in such a way that materials aretransformed.

REPRESENTATIVE OR MAIN-GROUPELEMENTS:

The 44 elements in Groups 1 through 8 on the periodic table of elements in the North American system, for which the number of valence electrons equals the group number. (The only exception is helium.) In the IUPAC system, these elements are assigned group numbers 1, 2, and 13 through 18. (In these last six columns on the IUPAC chart, there is no relation between the number of valence electrons and group number.)

SHELL:

The orbital pattern of the valence electrons at the outside of an atom.

SUBLEVEL:

A region within the principal energy level occupied by electrons in anatom. Whatever the number n of the principal energy level, there are n sublevels. At each principal energy level, the first sublevel to be filled is the one corresponding to the s orbital pattern, followed by the p and then the d pattern.

TRANSITION METALS:

A group of 40 elements, which are not assigned a group number in the version of the periodic table of elements known as the North Americansystem. These are the only elements that fill the d orbital. In addition, the transition metals—unlike the representative or main-group elements—have their valence electrons on two different principal energy levels. Though the lanthanides and actinides are considered inner transition metals, they are usually treated separately.

VALENCE ELECTRONS:

Electrons that occupy the highest principal energy level in an atom. These are the electrons involved in chemical bonding.

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