Families of Elements***Pull out your Periodic
Tables!
Chapter 4.3
How are elements classified?• Two main groups: Metals and Nonmetals • Third group that is often used as a branch
off Nonmetals: Semiconductors (Metalloids)
What are the differences?• Metal an element that is shiny and
conducts heat and electricity well • Nonmetal an element that conducts
heat and electricity poorly • Semiconductor an element or
compound that conducts electric current better than an insulator but not as well as a conductor does
Let’s look more into metals…• Alkali metals
– Elements from Group 1 on the Periodic Table (on the very left!)
– Characteristics: soft, shiny, reacts violently with water• Very reactive because they have one valence
electron• Combine with other elements to form
compounds– Example: Na (sodium!!)
• Combines with Cl to make table salt (NaCl) – “That’s salty!!” -Mr. Parker
Alkaline-Earth Metals• Elements from Group 2 on the
Periodic Table (2nd column from the very left!)
• Have 2 valence electrons—so still reactive and may lose 2 electrons to form positive ions with a +2 charge
• Often combine with other elements to form compounds
Alkaline-Earth Metals
• Examples: – Calcium:
• Hard shell of sea animals • Limestone- Corals • Marble
– Magnesium: • Lightest of all structural metals—
used in some airplanes • Used in milk of magnesia (medicine)
Transition Metals • Located in Groups 3-12 of the Periodic Table • Much less reactive • Called “transition metals” because they
transition to having properties similar to Group 2 elements to having properties of Group 13 elements
• Examples: Gold, Silver, Copper, Iron, Mercury
Mercury• Unique because it is the only metal
liquid at room temperature • Harmful because you can breathe in the
vapors, which accumulate in your body…and are toxic!
Synthetic “Manmade” Elements• Includes all elements with atomic
numbers greater than 92 • Made for many different reasons• Examples:
– Technectium –can be used to diagnose cancer in soft tissues of the body
– Promethium- in some “glow in the dark” paints
– Americium—small amount found in smoke detectors
Nonmetals • Located on the right side of the
Periodic Table (except for Hydrogen) • Include some elements in Groups 13-
16, and all elements in Groups 17 and 18
Characteristics of Nonmetals• Generally will form negative ions by
gaining electrons by combining with other elements
• Nitrogen and oxygen are the most plentiful gases in the air
• Examples: – Oxygen ion: Oxide: O-2
– Nitrogen ion: Nitride: N-3
– Sulfur ion: Sulfide: S-2 has a rotten smell
Carbon- A nonmetal • Why is carbon useful?
– Found almost everywhere! • Examples:
– As graphite (pencil lead)—pure form – As diamond –pure form – Combined with other elements as:
• Glucose C6H12O6
• Gasoline C8H18
The Halogens• Elements found in Group 17• A group of nonmetals that are very reactive!
– Want to gain electron to fill outer energy levels!
• Examples: – Chlorine in ion form: Chloride ion: Cl-
• Combines with sodium (Na) to form NaCl – Iodine in ion form: Iodide ion: I-
• Added to table salt to make “ionized salt” – Fluorine in ion form: Fluoride ion: F-
• Used in many toothpastes to prevent tooth decay
Noble Gases• Elements located in Group 18• They are “inert” (nonreactive)
– Because they have a filled outer energy level – Therefore they do not need to combine with
other elements and so can be found in nature as single atoms instead of as molecules
• Examples: – Neon—used for bright colors – Helium—in blimps and balloons to help objects
‘float’ since He is less dense than air – Argon—used to fill light bulbs
Semiconductors• Also referred to as metalloids • Clustered towards the right side of the
Periodic Table• Includes only 6 elements: boron,
silicon, germanium, arsenic, antimony, and tellurium
Semiconductors• Although classified as nonmetals, each
semiconductor has some properties of metals – Able to conduct heat and electricity under
certain conditions • Examples:
– Boron—added to steel to increase hardness and strength; used to make heat-resistant glass
Silicon- A Semiconductor• Accounts for 28% of the mass of
Earth’s crust • Combines with oxygen to make silicon
dioxide, SiO2 (sand!) • Silicon chips are the basic building
blocks of computers