Section 4: Nonmetals and Metalloids

• Objectives: locate nonmetals and

metalloids in the periodic table

compare the physical and chemical properties of nonmetals with those of metals, and describe the properties of metalloids

What is a Nonmetal?

•The element on the right side of the zigzag line are nonmetals. (yellow boxes)

•An element that does not have most of the properties of metal.

Physical Properties of Nonmetals

•low melting point-many are gases at room temperature

•Few are solids at room temperatureExamples: Sulfur, carbon, and iodine

•Only bromine is a liquid at room temperature.•Most physical properties of nonmetals are opposite of the metals;

-dull, not shiny-solid nonmetals are brittle (not malleable and not ductile)-poor conductors of heat and electricity.

Chemical Properties of Nonmetals

•Except for Group 18 most form compounds

-able to gain or share electrons (usually do not loose electrons)

-Group 18 has full valence shellsdo not easily loose or share

electrons

Compound of Nonmetals•Nonmetals usually react with metals

•Valence electrons move from the metal atoms to the nonmetals•Example: table salt (NaCl)

•sodium has 1 valence electron and chlorine has 7

•Nonmetals can form compounds with other nonmetals

•forms diatomic molecules •such as oxygen and hydrogen

Families of Nonmetals

•Carbon only nonmetal is this family•Silicon and germanium are metalloids•Tin and lead are metal•Contain 4 valence electron

•Carbon is most important in chemistry of living things·All living thing made up of carbon.

•Diamonds and soot are both forms ofcarbon.

Diamonds are the hardest material materials. It is used as a jeweland for saws, drills, and files.

Soot is very soft. It is used as pigment in paints and crayons

Nitrogen Group

•Contain 5 valence electrons•80% of atmosphere is nitrogen•Most living things get nitrogen from food eaten

•Some bacteria use nitrogen from the air

•Phosphorus is in nitrogen group•Not stable as element•Must combine with other elements to form compounds

Oxygen Group

•Elements in this group share or gain 2Electrons

•Group contains 3 nonmetals•Important gas for all living things•Oxygen is most abundant element is

Earth crust and 2nd most abundant element in earths atmosphere

•Sulfur is nonmetal in oxygen family•Used in production of rubber bands, tires, and medicines

Halogen Family

•All elements have 7 electron•Usually gains or shares one electron

•All elements are nonmetals•Very reactive

•Dangerous to humans in pure form

Halogens•Fluorine used in nonstick cookware

and fluoridation of water to fight tooth decay

•Chlorine is used as disinfectant•found in table salt

•Bromine is used in compound of silver bromide that is used in photographic film.

•Iodine is used as disinfectant

Noble Gases

•Valence shell is full with 8 electrons•Very stable and unreactive

•All are found in earth’s atmosphere insmall amounts

Hydrogen Stands Apart

•1 proton and 1 electron•however chemical properties

are so different it is not grouped into a family

•90% of atoms in universe arehydrogen, but only 1% ofmass of crust, oceans, andatmosphere is hydrogen

•Rarely found on earth as pureelement

Metalloids

•Areas shaded in green are metalloids

•Have some characteristics ofmetals and some of nonmetals

•Silicon and germaniumare used to

makesemiconductor

•Most useful property of metalloidis ability to conductelectricity

•Semiconductors carry electricityunder some conditions andduring other conditionscannot carry electricity

Used in computer chips, transistors, and lasers.