Bell Work Using your textbook, define the following terms: Metalloid Semiconductor Allotrope.

Bell Work

Using your textbook, define the following terms:•Metalloid•Semiconductor•Allotrope

Section 3 Mixed Groups

Objectives

• Distinguish among metals, nonmetals, and metalloids

• Describe the nature of allotropes• Describe how the properties of metalloids define

them as semiconductors

Properties of Metalloids• Form ionic and covalent bonds with other elements • Have metallic and nonmetallic properties• Semiconductor: def. element that conduct electric current

under certain conditions • Mixed groups- 13,14,15,16,17 contain a combo of metals,

nonmetals, and metalloids

Boron Group• All have 3 electrons in outer shell

BORON, B - metalloid• Borax used in some laundry

products to soften water• Boric acid mild disinfectant• Boranes used in jet and rocket

fuel

Boron Group conti.ALUMINUM, Al – metal•most abundant metal in Earth’s crust•strong, lightweight•used in cooking pans, siding, airplanes

Carbon Group• 4 electrons in outer shell• Allotropes- def. different forms of the same

element; different molecular structure

Carbon, C – nonmetal• found in all organic compounds• CO2

• natural gas• coal & oil

Use Phone…

• Soft lead metal was once used for writing black marks on paper. Graphite mixed with clay is less toxic and has replaced lead in pencils for writing.

• The term graphite comes from the Greek word ____________ which means ___________________.

GrapheinTo write

Allotropes in CarbonDiamond- clear, extremely hard•each C is bound to 4 C atoms forming tetrahedronsGraphite- black powder consisting of hexagonal layers of C atoms where each C is bound to 3 CBuckminsterfullerene- soccer ball shape•used to make tiny tubes nanotubes•https://www.brainpop.com/technology/scienceandindustry/nanotechnology/

Carbon group conti.Silicon, Si - metalloid•2nd most abundant element in earth’s crust•most found in sand, rocks, and soil•2 allotropes: 1.hard, gray substance 2.brown powder•Used in electronic devices ex: computer chips Germanium, Ge – metalloid•Semiconductor used in cell phone and other electronics

Tin, Sn- metal

•Coats other metals to prevent corrosion

•combines w/ other metals to produce bronze

Lead, Pb- metal

•once used in paint and pencils TOXIC

Nitrogen Group• 5 electrons in the outer shell

• Tend to share electrons and form covalent compounds w/ other elements

Nitrogen, N – nonmetal • 4th most common element in body

• Used to produce nitrates (NO3-)

and ammonia found in fertilizers

Phosphorus, P- nonmetal• 3 allotropes

• water softener, fertilizers, match heads, fine china

Nitrogen Group conti.

• Antimony, Sb (metalloid)& Bismuth, Bi (metal)- used to lower melting point in other metals

• Bismuth used in automatic fire-sprinkler heads

Oxygen Group • 6 electrons in outer shell

Oxygen, O - nonmetal • 21% air, diatomic molecule O2 (needed for

respiration)• electrical storm O2 ozone molecules O3

(protection from Sun’s radiation)

Oxygen Group cont.Sulfur, S – nonmetal•several allotropes: different shaped crystals & noncrystalline forms•Bad smell- rotten eggs!•pigments in paint•Sulfuric acid fertilizersSelenium, Se – nonmetal•need trace amounts in diet for making antioxidant enzymesTellurium, Te – metalloid•brittle, mildly toxic, rare, silver-white; alloy, no biological functionPolonium, Po – metalloid•Rare radioactive element

HOMEWORK• Chapter Review Worksheet

Synthetic Elements• By smashing existing elements with

particle accelerated in a heavy ion accelerator, nuclear scientists have been creating elements typically not found on Earth.

• Except for Technetium 43 and Promethium 61, each synthetic elements has more than 92 protons (transuranium elements).

• Neptunium-> bombarding U w/ neutrons; ½ disintegrate in 2 days to form plutonium (highly toxic/used in bombs)

• Pu-> changed to Americium (used in smoke detectors)

Transuranium Elements• Unstable

• Synthetic

• Many disintegrate quickly

• Towards the bottom of the periodic table

• More than 92 protons

Why make elements?• Medical applications

• Weapons applications

• By studying how these elements form and disintegrate, gain understanding of forces holding the nucleus together. When atoms disintegrate = radioactive

• Scientists are seeking stability in synthetic elements