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

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