Elements and Their Properties

1. Elements and Their Properties

2. What Makes an Element Reactive? • An incomplete valence electron level. • All atoms (except hydrogen & helium) want to have 8 electrons in their very outermost energy level (This is called the rule of octet.) • Atoms bond until this level is complete. Atoms with few valence electrons tend to lose them during bonding. • Atoms with 5, 6 or 7 valence electrons tend to gain electrons during bonding.

3. Metals • Metal: Elements are usually solids at room temperature. • Mercury is an exception. • They are good conductors of heat and electricity. • They have luster (reflect light). • Metals are malleable, meaning they can be hammered and rolled into sheets. • Metals are ductile, meaning they can be drawn into wire. • Most elements are metals.

4. Ionic Bonding in Metals • Atoms of metals usually have one to three electrons in their valence shell. • Because of this, they tend to give valence electrons away when bonding with a nonmetal. • This forms an ionic bond. • This makes them both stable.

5. Metallic Bonding in Metals • Metallic bonding is not ionic, because no electrons are given, taken, or even shared (a covalent bond). • The valence electrons flow freely among the positively charged nuclei and form a cloud around the ions of the metal. • Metals are good conductors of electricity because the valence electrons are weakly held. • http://www.drkstreet.com/resources/metallic-bonding-animation.swf

6. Alkali Metals • The alkali family is found in the first column of the periodic table. • Atoms of the alkali metals have a single electron in their outermost energy level, in other words, 1 valence electron. • They are shiny, have the consistency of clay, and are easily cut with a knife.

7. Alkali Metals • They are the most reactive metals. • They react violently with water. • Alkali metals are never found as free elements in nature. They are always bonded with another element. • http://www.youtube.com/watch?v=YvSkXd_VVYk&NR=1&feature=fvwp

8. Uses of Alkali Metals • Alkali metals and their compounds are necessary for living things to stay healthy. • Potassium and sodium compounds are necessary for the nervous system and muscular system to function correctly. • Lithium is sometimes used to treat imbalances in the brain. • Rubidium and Cesium compounds are used in photocells.

9. Radioactive • Francium, the last element of the alkali metals is rare and radioactive. • A radioactive element is one in which the nucleus breaks down and give off particles and energy. • Francium is so rare that only 25 to 30 grams of it are in Earth’s crust at a time (within uranium minerals. • It has never been isolated as the pure element. • As it is so radioactive, any amount formed would decompose to other elements.

10. Alkaline Earth Metals • Alkaline earth metals are the second column on the periodic table (Group 2) • They are reactive metals that are always combined with nonmetals in nature. • Several of these elements are important mineral nutrients (such as Mg and Ca). • Many are used in the production of fireworks.

11. Alkaline Earth Metals in Your Body • Calcium phosphate is necessary for healthy bones. • Barium sulfate is used as a tracer for finding problems in the digestive tract because it absorbs x-rays so well. • Radium is found with uranium and was once used as a radioactive treatment for cancer.

12. Transition Metals • Elements in groups 3-12 • Less reactive, harder metals • Includes metals used in jewelry and construction • Metals in this family are used as metals.

13. Transition Metals • The compounds of transition metals are usually brightly colored and are often used to color paints. • Transition elements have 1 or 2 valence electrons, which they lose when they form bonds with other atoms. Some transition elements can lose electrons in their next-to-outermost level.

14. Transition Metals • Transition elementshave properties similar to one another and to other metals, but their properties do not fit in with those of any other family. • Many transition metals combine chemically with oxygen to form compounds called oxides. Iron oxide—rust—on iron

15. Iron, Cobalt, Nickel • The three are called the iron triad because they are used to make steel and other metal alloys. • Iron is the most widely-used metal. • Nickel is added for strength and as plating for shine. • Cobalt added to glass or glaze gives it a blue color.

16. Copper, Silver, Gold • In Group 11 • They are stable, very malleable, and can be found in their purest form in nature. • Used in the past as coin metals—too expensive now. • Most coins are now copper and nickel alloys (mixtures of metals). • Copper used for wiring due to its ability to conduct. • Silver compounds were once used to help develop photographs (before the digital age). • Silver and gold are used in jewelry due to their beauty, resistance to corrosion, and relative rarity.

17. Copper, Silver, Gold

18. Zinc, Cadmium, Mercury • In Group 12 • Zinc and cadmium are often used as plating materials (coating) over other metals because they have protective qualities. • Cadmium is used in rechargeable batteries. • Mercury is used in thermometers, thermostats, batteries, and CFL bulbs. • They are all toxic. • Mercury is also a bi-product of coal burning and other industry. The sludge can leach into groundwater. Mercury poisoning can lead to neurological damage and death. • While zinc is a necessary element for the body, too much is dangerous.

19. Zinc, Cadmium, Mercury How a mercury thermostat works

20. Rare Earth Elements • The thirty rare earth elements make up the lanthanide (row 1) and actinide (row 2) series. • One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made. • Magnets made from rare earth elements are some of the strongest.

21. Rare Earths: Lanthanides • Atomic numbers 58 – 71 • La, Ce, Pr, and Sm bonded with carbon are used in the motion picture industry for making special lenses and lamps. • Eu, Gd, and Tb are used in nuclear reactors and also to produce the colors in televisions when an electron beam hits them.

22. Rare Earths: Actinides • Atomic numbers 90 - 103 • All are radioactive and unstable • Difficult to study • Thorium is used to make high-quality, distortion-free camera lenses. • Uranium is used in nuclear reactors and in nuclear weapons. • Uranium glass glows under black light.

23. METALS IN THE CRUST • Many of the metals we use are found in ores within Earth’s crust. • To separate a metal from other elements, chemicals and heat must be added. • Adding heat is called roasting. • Chemicals and heat together are called smelting. • The process of mining and smelting is quite expensive. • Google Earth

25. Nonmetals • Nonmetals : • are elements that usually are gases or brittle solids at room temperature. • do not usually conduct heat or electricity well. • are generally dull in luster. • are found in the upper right hand corner of the periodic table, plus hydrogen.

26. Bonding in Nonmetals • Electrons in nonmetals are strongly attracted to the nucleus. • Because of this, the electrons don’t move away as easily, so they don’t conduct electricity well. • They can form both ionic bonds—where electrons are given or taken—or covalentbonds—where electrons are shared between atoms. • When nonmetals bond with a metal, ionic bonds are formed. • When nonmetals bond with other nonmetals, covalent bonds are formed.

27. Hydrogen • Hydrogen belongs to a family of its own. • Hydrogen is a diatomic, reactive gas. Two atoms of it H bond together in nature. • Hydrogen was involved in the explosion of the Hindenberg. It is very reactive—group 1. • Hydrogen is promising as an alternative fuel source for automobiles http://www.youtube.com/watch?v=F54rqDh2mWA http://www.youtube.com/watch?v=CgWHbpMVQ1U&feature=fvwp

28. Hydrogen • Hydrogen can gain an electron when it bonds with an alkali metal or an alkaline earth metal to form hydrides. • Hydrogen only needs 2 electrons to fill up its single valence shell, so, technically, it can’t reach the “rule of octet.”

29. Halogens • Halogens are in group 17 and have 7 valence electrons, which explains why they are the most active non-metals. Always found combined with other elements in nature. • They are very reactive diatomic nonmetals.

30. Halogens • Halogen atoms only need to gain 1 electron to fill their outermost energy level. • They react with alkali metals to form salts. • Fluorine is the most reactive element of all elements. • It is used in compounds to: • prevent cavities • etch glass • It was once used in a compound with carbon (fluorocarbon) in refrigeration and as a propellant in aerosol cans, but it was found to damage the ozone layer.

31. Halogens • Chlorine, the most abundant halogen, is extracted from seawater. • Used as a disinfectant—bleach. • Bromine is the only nonmetal that is liquid at room temperature and is also extracted from seawater. • Used as a disinfectant • Bromine compounds are used as cosmetic dyes.

32. Halogens • Iodine is solid, shiny, and purple and vaporizes when heated—sublimation. • Iodine is necessary for producing thyroxin in the body and helps keep the thyroid gland healthy. • Astatine is radioactive with no known uses (because it’s rare).

33. Noble Gases • Noble gases exist by themselves in nature due to their valence level meeting the rule of octet without bonding. • They can be forced to bond with other elements in a laboratory. • Helium is a stable gas. • Used in blimps and balloons • Used in certain welding applications generally where the metals welded are not iron. • Neon and argon are used in “neon” signs. • Argon and krypton are used in electric light bulbs to produce light in lasers.

34. Section 3: Mixed Groups

35. Metalloids • Groups 13 through 16 have some metals, some metalloids, and some nonmetals—often within one family. • A metalloid is a type of matter that can have metallic and nonmetallic properties. • They can form ionic or covalent bonds. • They can conduct electricity better than nonmetals, but not as well as some metals. • Except for aluminum, they touch the zigzag line on the periodic table.

36. Boron Family • Elements in group 13 have 3 valence electrons. • Includes metals and one metalloid—Boron. • Aluminum, the most abundant metal in Earth’s crust, was once considered rare and expensive-- not a “disposable metal.”

37. Carbon Family • This family includes a non-metal (carbon), metalloids, and metals. • Carbon has many forms, some of which are • Radioactive • Diamond • Graphite • Buckminsterfullerene • Elements in group 14 have 4 valence electrons. • Contains elements important to life--and computers. • Carbon is the basis for an entire branch of chemistry (organic chemistry). • Silicon and Germanium are important semiconductorsused in computer chips. • Semiconductors will conduct electricity under certain conditions.

38. Carbon Family • Silicon dioxide is found in Earth’s crust—in sand and rocks. • Its structure is crystal, similar to a diamond. • Silicon, a metalloid, occurs as 2 allotropes. • An allotrope are different forms of the same element, where the atoms arrange in different ways. • Silicon can occur as a hard, gray substance or a brown powder.

39. Carbon Family • Tin is used to coat other metals (tin cans) and in alloys, like bronze. • Germanium, the other metalloid in the carbon family, is used with silicon in making semiconductors.

40. Carbon Is Amazing! • Carbon has several allotropes, including: • Graphite • Diamond • Buckminsterfullerine • Nanotubes • What makes an allotrope an allotrope is how the atoms of an element come together as a larger mass.

41. Carbon Family Ant (carbon-based organism) holding microchip (probably made of germanium or silicon)

42. Nitrogen Family • Antimony, a metalloid, and bismuth, a metal are able to lower the melting point of other metals. • Bismuth is used in fire-sprinkler heads because of this. • Elements in group 15 have 5 valence electrons. • They tend to share electrons when they bond. • This family includes non-metals, metalloids, and metals. • Nitrogen makes up over 75% of the atmosphere. • Nitrogen and phosphorus are both important in living things. • The red stuff on the tip of matches is phosphorus. • http://www.youtube.com/watch?v=rPbE2KSPxuU&feature=related • http://www.youtube.com/watch?v=1DxLwZhTj0A

43. Oxygen Family • Elements in group 16 have 6 valence electrons. • Oxygen, as O2, is necessary for respiration, and O3 helps protect Earth from radiation. • Many things that stink, contain sulfur (rotten eggs, garlic, skunks, etc.). • Most elements in this family share electrons when forming compounds. • Oxygen is the most abundant element in the earth’s crust. It is extremely active and combines with almost all elements.

44. Oxygen Family • Selenium is needed by the body’s immune system in small amounts. It is also used in photocopiers due to its conductive properties, and in solar cells. • Selenium is used as a key ingredient in some dandruff shampoos.

45. Synthetic Elements • New elements have been made by humans. • They are made by bombarding existing elements with particles that have been accelerated at high rates of speed in a particle accelerator. • Uranium is bombarded with neutrons to make neptunium. • Neptunium disintegrates into synthetic plutonium. • Plutonium can be synthesized into americium. • Americium is used in smoke detectors.

46. Synthetic Elements • Making elements is expensive, however, the value of them in medicine and other applications often offsets the cost. • In 1999, element 114 was discovered and held together for 30 seconds—which is a long time for most synthetic elements! • Plutonium and 9 other “synthetic” elements have since been found naturally in very small amounts on Earth. All, except francium, were synthesized before they were found in nature! • Technically then, elements 1-98 are naturally occurring.

47. Transuranium Elements • Elements having more than 92 protons (more than uranium) are called transuranium elements. • All of them are unstable, and many of them disintegrate (decay) quickly into other elements. This means they are all radioactive.