Download 4-3 Families of Elements

4-3: Families of Elements
Tuesday, August 18, 2015
5:49 PM
Key Terms:
1. Metal - an element that is shiny and conducts heat and electricity well
2. Nonmetal - an element that conducts heat and electricity poorly
3. Semiconductor - an element or compound that conducts electricity better than an insulator but not as well as a
conductor does
4. Alkali metal - one of the elements of Group 1 of the periodic table
5. Alkaline-earth metal - one of the elements of Group 2 of the periodic table
6. Transition metal - one of the elements of Groups 3-12 of the periodic table
7. Halogen - one of the elements of Group 17 of the periodic table
8. Noble gas - an unreactive element of Group 18 of the periodic table
I. How Are Elements Classified?
a. Elements are classified into three groups
i. Most elements are metals--they are shiny solids that can be stretched and shaped.
ii. All nonmetals, except for hydrogen are found on the right side of the periodic table.
iii. Nonmetals that can sometimes conduct heat/electricity are called semiconductors or metalloids.
II. Metals
a. The alkali metals are very reactive
i. Very reactive because they have one valence electron that can easily be removed
to form a positive ion
ii. Because they are so reactive, they are not found in nature as elements--they
combine with other elements to form compounds
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b. Alkaline-earth metals form compounds that are found in limestone and in the human body
i. Have two valence electrons
ii. Less reactive than alkali metals, but may still react to form positive ions with a 2+ charge.
iii. Calcium used in sea shells, limestone, marble, and coral
iv. Magnesium is the lightest of all structural metals--used to build airplanes, also found in medicines
Ch4 Atoms and the Periodic Table Page 1
c. Gold, silver, and platinum are transition metals
i. Transition metals are much less reactive than sodium or calcium, but they can lose electrons to form
positive ions, too.
ii. Transition metals can have more than one possible cation.
iii. Examples: gold, copper, iron, cobalt, manganese, and mercury
d. Technetium and promethium are synthetic elements
i. Technetium and promethium are both man-made, radioactive elements
ii. The last two periods of the transition metals are placed toward the bottom of the periodic table so
that similar elements elsewhere in the table still line up.
iii. All elements with atomic numbers greater than 92 are man-made
III. Nonmetals
a. Carbon is found in three different forms and can also form many compounds
i. Carbon can be in the form of graphite (pencil "lead"), diamonds, or fullerenes
ii. Carbon can combine with other elements to form millions of carbon-containing compounds
b. Nonmetals and their compounds are plentiful on Earth
i. Nonmetals may form compounds or gain electrons and form negative ions (anions).
ii. The most plentiful gases in the air are the nonmetals nitrogen and oxygen.
c. Chlorine is a halogen that protects you from harmful bacteria
i. Halogens are located in Group 17 of the periodic table.
ii. Halogens form compounds by gaining an electron to become negative ions.
iii. Often combine with alkali metals to form ionic compounds.
Ch4 Atoms and the Periodic Table Page 2
iii. Often combine with alkali metals to form ionic compounds.
d. The noble gases are inert
i. Noble gases exist as single elements instead of molecules.
ii. Noble gases are inert because their s and p orbitals are full of electrons.
e. Semiconductors are intermediate conductors of heat and electricity
i. Six elements are classified as semiconductors: boron, silicon, germanium, arsenic, antimony, and
tellurium.
ii. Able to conduct heat and electricity under certain circumstances.
Ch4 Atoms and the Periodic Table Page 3
f. Silicon is the most familiar semiconductor
i. Silicon atoms, usually in the form of compounds, account for 28% of the mass of Earth's crust.
ii. Sand and glass are made of the most common silicon compound, called silicon dioxide, SiO2
iii. Silicon is used in many hi-tech electronic devices
Ch4 Atoms and the Periodic Table Page 4