Chem-Phys, Chapter 19 Page 1 Chapter 19 – Elements and Their Properties

Chem-Phys, Chapter 19 Page 2 Properties of Metals 6,000 years ago, gold was the first metal used by man. Later, man used copper, silver, tin and iron. Metals are found on the left side of the periodic table (left of the zig-zag line). Metals are good conductors of heat and electricity.

Chem-Phys, Chapter 19 Page 3 Properties of Metals Most metals are solids. Metals reflect light. Metals are malleable (they can be pounded into a thin sheet) Metals are ductile (they can be pulled into a wire)

Chem-Phys, Chapter 19 Page 4 Metals Form Ionic Bonds Metals can usually lose between 1 and 3 electrons to form ions. Examples: –Ag 1+ –Fe 2+ –Fe 3+

Chem-Phys, Chapter 19 Page 5 Metals Form Metallic Bonds Metals are held together with metallic bonds. The atoms of the metal is surrounded by a “sea” of electrons. So, layers of metal atoms can shift without losing strength. The “sea” of electrons gives metals their conductivity.

Chem-Phys, Chapter 19 Page 6 Alkali Metals The alkali metals are in the first column of the periodic table. This column is called Group 1. All Group 1 elements have one outer electron which they lose when they form bonds. Na becomes Na + in NaCl, K becomes K + in KBr, etc. Alkali metals are the most reactive of the metals. They react with water.

Chem-Phys, Chapter 19 Page 7 Uses of Alkali Metals Compounds of sodium and potassium are necessary for life. Cadmium and rubidium are used in some photocells. Francium is radioactive and very rare. In a radioactive element, the nucleus breaks down and gives off particles and energy.

Chem-Phys, Chapter 19 Page 8 Alkaline Earth Metals Alkaline earth metals are in Group 2 of the periodic table. They are shiny, malleable, and ductile. Each atom of a alkaline earth metal has two outer electrons which it loses when it forms bonds. So, Ca becomes Ca 2+ when it forms CaCl 2, Mg becomes Mg 2+ when it forms MgSO 4, etc.

Chem-Phys, Chapter 19 Page 9 Uses of Alkaline Earth Metals Fireworks get their color from alkaline earth metals: strontium – red, magnesium – white, Barium – green, etc. Magnesium is used in airplanes, ladders, etc. Chlorophyll contains magnesium Calcium is found in marble and is necessary for strong bones. Barium is used in medical procedures.

Chem-Phys, Chapter 19 Page 10 Transition Elements The transition elements are in Groups 3 through 12 on the periodic table. These metals are at the “transition” between Group 2 and Group 13. These metals are the most familiar: –IronFeSilverAg –CopperCuGoldAu –NickelNiZincZn

Chem-Phys, Chapter 19 Page 11 Iron, Cobalt, Nickel Iron is the most widely used of all metals. Iron is the second most abundant metal behind aluminum. Steel is a mixture of iron and other metals such as cobalt and nickel. Nickel is used in nickels! Nickel is added to some metals to give them strength or to protect them.

Chem-Phys, Chapter 19 Page 12 Copper, Silver, and Gold Copper, Silver and Gold are in Group 11 on the periodic table. Coins are made of copper, silver, and gold. (U.S. not using gold or silver anymore.) These are called the coinage metals. Copper used in electrical wiring. Silver used in photographic film. Gold and silver are used in jewelry.

Chem-Phys, Chapter 19 Page 13 Zinc, Cadmium, and Mercury Zinc is used to protect other metals because it forms a thin protective oxide later. Cadmium is used in re-chargeable batteries. Mercury is the only metal that is a liquid at room temperature. It is used in thermometers and fluorescent lights. Mercury forms toxic compounds.

Chem-Phys, Chapter 19 Page 14 Inner Transition Elements The inner transition elements are the two disconnected rows of elements at the bottom of the periodic table. The lanthanides follow the element lanthanum. These elements are used in color TV screens. The actinides follow the element actinium. They are all radioactive and used in nuclear reactors and nuclear bombs.

Chem-Phys, Chapter 19 Page 15 Metals in the Earth’s Crust Gold, silver, and platinum are found as the metal in the earth’s crust. All other metals are found as ores. An ore is a compound of the metal. Before the metal can be recovered, metal ore must be separated from clay and rock. Ore is put through a chemical process, usually involving heat, to recover the metal.

Chem-Phys, Chapter 19 Page 16 Chapter 19, Section 1 Review 1.Describe the properties of a typical metal. 2.Identify the alkali metals and the alkaline earth metals. 3.Locate and describe the three separate groups of transition metals.

Chem-Phys, Chapter 19 Page 17 Non-metals Non-metals are found to the right of the zig-zag line. Non-metals are usually gases or brittle solids. Non-metals are not shiny and do not conduct electricity or heat well. Non-metals are usually not ductile or malleable.

Chem-Phys, Chapter 19 Page 18 Bonding in Non-metals Non-metals form both covalent and ionic bonds. Non-metals usually form ionic bonds when they react with metals (NaCl, AgBr, etc.) When bonded with other non-metals, non- metals usually form covalent bonds: H 2 O, NH 3, CH 4, etc.

Chem-Phys, Chapter 19 Page 19 Hydrogen About 90% of the atoms in the universe are hydrogen. When water is broken down by electrolysis, diatomic hydrogen, H 2, and diatomic oxygen, O 2 are released. Hydrogen can give up one electron like the alkali metals. Hydrogen is considered a non-metal.

Chem-Phys, Chapter 19 Page 20 Halogens The halogens are in Group 17. Halogen light contain small amounts of bromine or iodine. Chlorine is added to drinking water to kill germs. Fluoride is added to drinking water and toothpaste to strengthen teeth.

Chem-Phys, Chapter 19 Page 21 Halogens When a halogen reacts with a metal, they form a salt. For example, sodium and chlorine make sodium chloride, NaCl, table salt. Fluorine is the most chemically active element. Hydrofluoric acid (HF in water) is used to etch or frost glass.

Chem-Phys, Chapter 19 Page 22 Halogens The odor you smell near a swimming pool is usually chlorine. Bromine is the only non-metal that is a liquid at room temperature. Iodine is a shiny purple-gray solid recovered from seawater. Iodine can change directly from a solid into a gas. This is called sublimation.

Chem-Phys, Chapter 19 Page 23 Noble Gases The noble gases are found in Group 18. The noble gases occur as single atoms. They almost never react with anything to form chemical compounds. The noble gases are useful because they are so stable. Neon, argon, and krypton are used in electric lights and to make lasers.

Chem-Phys, Chapter 19 Page 24 Chapter 19, Section 2 Review 1.Is hydrogen a metal or a non-metal? 2.What are the properties of the halogens? 3.What are the properties and uses of the noble gases?

Chem-Phys, Chapter 19 Page 25 Properties of Metalloids The metalloids are the elements touching the zig-zag line at the right of the periodic table (aluminum is a metal). The metalloids have properties between those of non-metals and metals. Some metalloids are semi-conductors and useful in making transistors.

Chem-Phys, Chapter 19 Page 26 Boron Boron is contained in borax, a household laundry product. Boron is also in boric acid, a mild antiseptic. Boranes are found in jet and rocket fuel.

Chem-Phys, Chapter 19 Page 27 Carbon Group Carbon is a non-metal. Silicon and germanium are metaloids. Carbon is an element essential for life. Silicon occurs in two different forms that have different molecular structures, called allotropes: –A hard, gray solid –A brown powder

Chem-Phys, Chapter 19 Page 28 Carbon Group Silicon and germanium are semiconductors used in making the electronic devices and computers we all use. Tin is used in tin cans to prevent corrosion. Tin is combined with other elements to make bronze and pewter. Lead has many uses.

Chem-Phys, Chapter 19 Page 29 Allotropes of Carbon Carbon appears in three forms, called allotropes. Diamond – a clear, extremely hard form of carbon. Graphite – a black solid used in pencil lead. Buckminsterfullerene – spheres of carbon containing 60 atoms of carbon. Nanotubes of carbon.

Chem-Phys, Chapter 19 Page 30 Nitrogen Group The nitrogen family is in Group 15. All these elements have five electrons in the highest level orbital which are available for bonding. Nitrogen is an element essential for life. Nitrogen is contained in amino acids.

Chem-Phys, Chapter 19 Page 31 Nitrogen Group Phosphorous is a non-metal with three allotropic forms. Phosphorous is used in fertillizers. Antimony is a metalloid. Bismuth is a metal. Bismuth is used in alloys and used to lower their melting point.

Chem-Phys, Chapter 19 Page 32 Oxygen Group The oxygen family is in Group 16. Oxygen is essential for life. We need oxygen to breath. Oxygen occurs in two allotropic forms: –Oxygen gas, O 2 –Ozone gas, O 3, (“fresh” smell after a thunderstorm)

Chem-Phys, Chapter 19 Page 33 Oxygen Group The other oxygen group elements are non- metal selenium, and metalloids tellurium, and polonium. Selenium is necessary for life but toxic at high levels.

Chem-Phys, Chapter 19 Page 34 Synthetic Elements All elements above uranium (called the transuranium elements) are man-made. In a nuclear reactor, neutrons bombard uranium to make neptunium. Neptunium when bombarded by neutrons becomes plutonium. Plutonium when bombarded by neutrons becomes americium.

Chem-Phys, Chapter 19 Page 35 Synthetic Elements All synthetic elements are radioactive. Radioactive elements have uses in medical procedures. Radioactive americium is useful in smoke detectors. (Don’t throw a smoke detector away! It contains hazardous waste.)

Chem-Phys, Chapter 19 Page 36 Synthetic Elements Scientists also make synthetic elements to better understand how the nucleus operates. Scientists are looking for more stable elements above atomic number of 103. Element 114 has a half life of 30 seconds which is very long for these elements. Element 118 has been made.

Chem-Phys, Chapter 19 Page 37 Chapter 19, Section 3 Review 1.What are the differences between metals, non-metals, and metaloids? 2.What is the nature of allotropes? 3.What is the significance of differences in crystal structure in carbon? 4.What is the importance of synthetic elements?