HOW ARE ELEMENTS CLASSIFIED
Comparing Metals, Nonmetals, and Metalloids
Metals
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are good conductors of heat and electricity
have a shiny surface appearance
are easy to form and bend
Nonmetals
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are poor conductors of heat and electricity
have a dull surface appearance
are very brittle
Metalloids
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have some characteristics of metals and some characteristics of nonmetals
are semiconductors
METALS
The periodic table is arranged in such a way that the elements vary in a regular, or periodic, way from
right to left across the table. One property is the metallic nature of the elements. The elements on the
left side of the table are metals. Most metals generally have three or fewer electrons in the outermost
energy level of their atoms. Copper, gold, silver, and iron are examples of metals. Metals are malleable,
ductile, and have luster; most of the elements on the periodic table are metals. They oxidize (rust and
tarnish) readily and form positive ions (cations). They are excellent conductors of both heat and
electricity. The metals can be broken down into several groups.
The most chemically active metals are found in Group 1 (IA), the alkali metals. Alkali metals, such as
sodium and potassium, are reactive because their atoms have one valence electron. The most reactive
alkali metals are found at the bottom of Group 1 (IA). Atoms of Group 1 (IA) will easily give up their one
valence electron to have an outermost energy level that is filled. Atoms of Group 1, such as sodium (Na),
form ions with one positive charge (Na+). These must be stored under oil because they react violently
with water! They dissolve and create an alkaline, or basic, solution, hence their name. (lithium, sodium,
potassium, rubidium, cesium, and francium).
Alkaline-earth metals
The alkaline earth metals make up Group 2 (IIA). Alkaline earth metals, such as magnesium and calcium,
are not as reactive as the alkali metals. The atoms of the alkaline earth metals have two valence
electrons. To have a filled outer energy level, atoms of the alkaline earth metals will give up the two
valence electrons, forming an ion with a positive charge of two. For example, calcium (Ca) will form a
calcium ion with two positive charges (Ca2+). (beryllium, magnesium, calcium, strontium, barium, and
radium)
Transition metal – one of the metals that can use the inner shell before using the outer shell to bond.
Ionic solutions of these metals are usually colored, so these metals are often used in pigments. The
actinides and lanthanides are collectively called the rare earth elements and are filling the f orbitals.
They are rarely found in nature. Uranium is the last naturally occurring element; the rest are man-made.
NONMETALS
On the right side of the periodic table, the elements are nonmetals. Atoms of nonmetals usually have
five or more electrons in the outermost energy level of their atoms. Sulfur and oxygen are examples of
nonmetals.
Nonmetals lie to the right of the staircase and do not conduct electricity well because they do not have
free electrons. All the elemental gases are included in the nonmetals. Notice that hydrogen is placed
with the metals because it has only one valence electron, but it is a nonmetal. Nonmetals and their
compounds are plentiful on Earth.
Carbon is found in three different forms and can also form many compounds
Halogens
On the right side of the periodic table you can find the most active nonmetals, the halogens, which are
the elements in Group 17 (VIIA). The most reactive halogens are found at the top of Group 17 (VIIA). The
atoms of the halogens, such as bromine and chlorine have seven valence electrons. Halogens, like
fluorine (F), will gain an electron to fill the outermost energy level, forming a negative ion (F-). Known as
the “salt formers” because they combine with most metals to form salts; they are used in modern
lighting and always exist as diatomic molecules in their elemental form. Chlorine is a halogen that
protects you from harmful bacteria.
Noble Gases
Elements in a group share certain characteristics including similar chemical properties. For example,
Group 18 (VIIIA) is called the noble gas family. All the elements of the noble gas family have a filled
outer energy level; therefore, the noble gases do not readily react with other substances. The noble
gases are helium, neon, argon, krypton, xenon, or radon. Known for their extremely slow reactivity,
these were once thought to never react; neon, one of the noble gases, is used to make bright signs.
Metalloids/Semiconductors
If you look at a periodic table, you will see a zigzag line that divides the table. The elements located on
either side of this line are called metalloids/semiconductors because they have some properties of both
metals and nonmetals. Boron, silicon, germanium, and arsenic are examples of metalloids.
Semiconductors are intermediate conductors of heat and electricity under certain conditions.
Use the notes to complete the following statements.
1. The ____________________ states that when elements are listed in order of atomic number, similarities
in their properties will emerge in a regular pattern.
2. Because atoms of elements in the same group of the periodic table have the same number of
____________________, they have similar properties.
3. Some elements are ____________________ because their outermost energy levels are filled.
4. The valence electron of a lithium atom is easily removed to form a lithium ____________________ with
a charge of 1+.
5. Group 1 of the periodic table consists of the ____________________, a highly reactive group of
elements.
6. Atoms of alkaline-earth metals, such as calcium, have ____________________ valence electrons.
7. The ____________________ are located in the center of the periodic table.
8. The ____________________ are highly reactive elements located in Group 17 of the periodic table.
9. Noble gases are nonreactive gaseous elements that are located in Group ____________________ of the
periodic table.
10. The most familiar semiconductor, ____________________, is one of the most abundant elements in
Earth's crust.
11. Neon is an inert gas because its outer ____________________ is full of electrons.
12. Group 17 halogens form compounds by gaining an electron and forming a ____________________.
13. Nonmetals that can conduct heat and electricity under some circumstances are classified as
___________________.