Chapter 3 Elements and the Periodic Table Section

Chapter 3: Elements and the Periodic Table Section 4: Nonmetals and Metalloids

Nonmetal • An element that lacks most of the properties of a metal. • Most are poor conductors of electricity and heat and are reactive with other elements. Solid nonmetals are dull and brittle.

Physical Properties • State • 10 of 16 are gases at room temperature (O, N) • Others are solids (C, I, S) • 1 is liquid (Br) • Solid nonmetals are generally opposite of metals • Dull (not shiny) • Brittle (not malleable or ductile): break or crumble if hit with hammer • Lower densities • Poor conductors of heat and electricity

Chemical Properties • Reactivity • Most are reactive; readily form compounds • Fluorine (F) is the most reactive known element • Some, group 18, hardly ever form compounds • Electrons during reactions with other atoms • When nonmetals and metals react, electrons move from the metal to the nonmetal (Na. Cl) • When nonmetals form compounds with other nonmetals, they share electrons and become bonded together into molecules (CH 4)

Checkpoint 1 • What happens to the electrons in the atoms of nonmetals when they form bonds with other atoms?

Checkpoint 1 • What happens to the electrons in the atoms of nonmetals when they form bonds with other atoms? • They either gain or share electrons.

Families of Nonmetals • • • The Carbon Family The Nitrogen Family The Oxygen Family The Halogen Family The Noble Gases Hydrogen

The Carbon Family • Group 14 • Atoms can gain, lose, or share four electrons when reacting with other elements • Only carbon is a nonmetal • Carbon has an important role in the chemistry of life and fossil fuels

The Nitrogen Family • Group 15 • Two nonmetals: nitrogen and phosphorus • Usually gain or share three electrons when reacting with other elements • Nitrogen • Makes up 80% of atmosphere • Diatomic molecule: consists of two atoms • Nitrogen fixation by bacteria that turn it into useful form for plants • Phosphorus • Much more reactive, always found in compounds in nature • Used to make matches

The Oxygen Family • Group 16 • Contains three nonmetals: oxygen, sulfur, and selenium • Usually gain or share two electrons when reacting with other elements • Oxygen • • • Important to life Diatomic (oxygen you breathe) O 2 Sometimes triatomic (ozone) O 3 Can combine with almost every other element (very reactive) Most abundant in Earth’s crust, second-most abundant in atmosphere • Sulfur • Smells like rotten eggs • Used to make rubber, sulfuric acid

Checkpoint 2 • Which family of elements gains or shares three electrons?

Checkpoint 2 • Which family of elements gains or shares three electrons? • The Nitrogen family.

The Halogen Family Group 17 Fluorine (F), Chlorine (Cl) Halogen: salt forming All but astatine (At) are nonmetals Typically gain or share one electron when they react with other elements • Very reactive; dangerous in uncombined form • • • Fluorine (F) is most reactive, reacts with almost every known substance • Useful in compounds • Ex. Fluorine compounds added to water supply to help prevent tooth decay

The Noble Gases • Group 18 • Do not ordinarily form compounds because atoms of noble gases do not usually gain, lose, or share electrons (unreactive) • Found in small amounts in Earth’s atmosphere • Not discovered until the late 1800 s

Hydrogen • Simplest and smallest atom: one proton and one electron (some isotopes of hydrogen also have neutrons) • Very different from other elements; not in a family (hydrogen is not an alkali metal, even though it’s in the same column) • Makes up more than 90% of the atoms in the universe, but only 1% of the mass of Earth’s crust, oceans, and atmosphere • Rarely found as a pure element; usually in water molecules

The Metalloids • • Have some characteristics of both metals and nonmetals All are solid at room temperature Brittle, hard, and somewhat reactive Most useful property is their varying ability to conduct electricity • Conductivity depends on temperature, exposure to light, or the presence of small amounts of impurities • Used to make semiconductors (substances that can conduct electricity under some conditions but not under other conditions) in computer chips, transistors, and lasers. • Most common is silicon (Si), which forms a compound with oxygen to make sand glass

Checkpoint 3 • Which family of nonmetals is unreactive?

Checkpoint 3 • Which family of nonmetals is unreactive? • The noble gases.

Post-lesson Quiz 1. Which is not a property of nonmetals? a. shininess b. dullness c. brittleness d. poor conductivity

Post-lesson Quiz 2. Where are nonmetals generally located on the periodic table? a. on the right side b. in the middle c. on the left side d. interspersed throughout

Post-lesson Quiz 3. Some metalloids can conduct electricity under some conditions, but not others. Because of this, these metalloids are sometimes called… a. pseudo-conductors b. semiconductors c. hemiconductors d. biconductors

Post-lesson Quiz 4. Which element is the simplest and is not part of a family? a. helium b. lithium c. boron d. hydrogen

Post-lesson Quiz 5. What happens when nonmetal atoms form bonds with other atoms? a. they lose electrons b. they always gain electrons c. they sometimes gain and sometimes share electrons d. they always share electrons