Chapter 5: The periodic Table Section 3: Families of Elements

Objectives What does each element family have in common? What are the families of metals? What are some of the families of nonmetals? What are semiconductors?

Classifying Elements Further What does each element family have in common? In general, the elements in a family have the same number of valence electrons.

Metals What are the families of metals? Families of metals include the alkali metals, the alkaline-earth metals, and the transition metals. alkali metal: one of the elements of Group 1 of the periodic table alkaline-earth metal: one of the elements of Group 2 of the periodic table transition metal: one of the metals that can use the inner shell before using the outer shell to bond

Metals, continued The alkali metals are very reactive. Alkali metals are in Group 1, on the left edge of the periodic table. They are reactive because they have one valence electron that is easily removed. They are soft and shiny, and many have similar melting points, boiling points, and densities.

Metals, continued Alkaline-earth metals form compounds that are found in limestone and in the human body. Alkaline-earth metals are in Group 2. Alkaline-earth metals are less reactive than alkali metals, but still react to form positive ions. In general, alkaline-earth metals are harder, denser, stronger, and have higher melting points than alkali metals.

Metals, continued Transition metals are in the middle of the periodic table. With the exception of mercury, transition metals are harder, more dense, and have higher melting points than alkali metals and alkaline-earth metals. They are also less reactive, but they can form positive ions.

Nonmetals What are some of the families of nonmetals? Families of nonmetals include the noble gases and the halogens. noble gas: one of the elements of Group 18 of the periodic table halogen: one of the elements of Group 17 of the periodic table

Nonmetals, continued The noble gases are relatively inert. The noble gases are in Group 18. They exist as single atoms instead of as molecules. They are inert, or unreactive, because their s and p orbitals are filled. In general, they do not form ions or compounds.

Nonmetals, continued The halogens combine easily with metals to form salts. The halogens are in Group 17. With the addition of a single electron, halogens become stable. They combine easily with metals (especially alkali metals) to form salts.

Nonmetals, continued Nonmetals and their compounds are plentiful on Earth. Six other nonmetals are on the right side of the periodic table. Carbon can form many compounds. There are millions of carbon- containing compounds.

Semiconductors What are semiconductors? As their name suggests, semiconductors are able to conduct heat and electricity under certain conditions. Semiconductors are also called metalloids.