ELEMENTS and THEIR PROPERTIES Chapter 19

THE PERIODIC TABLE( pages in text)

The Periodic Table In the late 1800’s Dmitri Mendeleev, a Russian chemist, discovered a way of organizing the elements. This became known as the first periodic table. He put the elements in order by their atomic mass, today we have them in order of their atomic number. He left blank spaces in his table to keep the elements lined properly. He new from this that there were elements not yet discovered.

Properties of metals 1.conduct heat and electricity 2.Luster- reflect light well 3.Malleable- can be hammered or rolled into sheets 4.Ductile- can be drawn into wires 5.Ionic bonding- combine with non-metals by losing electrons 6.Metallic bonding- positively charged metallic ions are surrounded by a cloud of electrons; ions are in sliding layers and electrons are weakly held; readily form ionic bonds with non-metals.

The Alkali Metals- softer and more reactive then other metals Highly reactive with oxygen and water; don’t occur naturally as elements forms. Combine readily with other elements due to single electron in outer energy levels Multiple uses: Human health- sodium, potassium, and lithium compounds Photocells- some depend on rubidium or cesium Francium- a radioactive element which breaks down giving off particles and energy.

The Alkaline Earth Metals- not found naturally in element form; two electrons in outer energy level Applications- strontium and magnesium found in fireworks; magnesium in vehicles, ladders, and bats; calcium in statues and countertops Human Body- calcium in bones; barium in disease diagnoses; radium formelrly used in cancer treatment

Transition Elements- they often occur in nature as uncombined elements Typically form colored compounds- chromium found in rubies and emeralds Iron triad- iron, cobalt, and nickel iron- most widely used of all metals and main ingredient in steel; abundant in Earth’s crust Cobalt and Nickel- used in some steels Nickel- used to coat other metals

Copper, silver, and gold- coinage metals since once were commonly used in coins Copper- used in electric wiring because it is a superior electricity conductor Silver- used in photographic film and paper; jewelry Gold- used in jewelry

Zinc, cadmium, mercury- group 12 on the periodic table Zinc and cadmium- often used to coat or plate other metals. Mercury- only room temperature metal; used in thermometers and batteries

The inner Transition metals- seem disconnected from the rest of the periodic table The Lathanides- include lanthanum, cerium, praseodymium, amarium, europium, gadolinium, and terbium. The Actinides- all are radioactive and unstable; uranium is the best known. The Lathanides- include lanthanum, cerium, praseodymium, amarium, europium, gadolinium, and terbium. The Actinides- all are radioactive and unstable; uranium is the best known.

NONMETALS PROPERTIES OF NONMETALS- usually gases or brittle solids at room temperature; are not malleable or ductile; usually poor conductors of heat and electricity; usually not lustrous Ionic compounds- form when nonmetals gain electrons from metals and become negative ions Covalent compounds- form when nonmetals share electrons with other nonmetals.

Hydrogen - most common element in the universe. A diatomic molecule- two atoms of the same element in a covalent bond Highly reactive element found in mostly on Earth as part of a water compound.

The Halogens- include Bromine, iodine, fluorine, chlorine, and astatine A salt forms when a halogen gains one electron from a metal Use of halogens: chlorine- disinfectant and bleach Bromine- dyes in cosmetics Iodine- hormone regulation Sublimation- a solid changes directly into a gas without it first becoming a liquid

The noble gases- exist as isolated, stable atoms Helium- used in blimps and balloons Neon, argon, and krypton- used in lights

Properties of metalloids- form ionic and covalent bonds; have some metallic and some non-metallic properties; partial conduction gives them semiconductor characteristics.

The Boron group- named for the first element in group 13 Boron- used in water softening products; antiseptics and fuels Aluminium- abundant in Earth’s crust; used in cans, foil wrap, pans, building materials’ and aircraft

The Carbon Group- four electrons in outer energy level Carbon- found in coal, oil, natural gas and foods Silicon occurs as an allotrope- same element with different molecular structures silicon is found in sand, rocks, and soil The main component in semiconductors, which conduct electricity under certain conditions Continued…

Germanium- also used in semiconductors Tin- used to coat other metals Lead- toxic, so no longer used in paint Diamonds, graphite, and buckminsterfullerene are all allotropes of carbon

The Nitrogen group- five electrons in outer energy level; tend to form covalent bonds Nitrogen- used to make nitrates and ammonia Phosphorus- used in water softners, fertilizers, match heads, and fine china Antimony and bismuth used with other metals to lower their melting points

The Oxygen group of group 16 Oxygen- makes up 20% of air, is used by living things in respiration, and provides protection from the Sun’s radiation. Sulfur- used to form sulfides for pigment in paint. Selenium- used in photocopiers and multivitamins Tellurium and polonium are also oxygen group elements.

Synthetic elements- scientists create elements not usually found on Earth; synthetic elements usually disintegrate quickly.