Elements and Their Properties

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.

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.

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.

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

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.

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

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.

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.

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.

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.

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.

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.

Transition Metals• Transition elements have

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

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.

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.

Copper, Silver, Gold

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.

Zinc, Cadmium, Mercury

How a mercury thermostat works

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.

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.

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.

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

Nonmetals

• Nonmetals :1. are elements that usually are gases or

brittle solids at room temperature.2. do not usually conduct heat or electricity

well.3. are generally dull in luster.4. are found in the upper right hand corner

of the periodic table, plus hydrogen.

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 covalent bonds—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.

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=F54rqDh2mWAhttp://www.youtube.com/watch?v=CgWHbpMVQ1U&feature=fvwp

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.”

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.

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.

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.

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).

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.

Section 3: Mixed Groups

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.

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.”

Carbon Family• 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 semiconductors used in computer chips.

• Semiconductors will conduct electricity under certain conditions.

• This family includes a non-metal (carbon), metalloids, and metals.• Carbon has many forms, some of which are

•Radioactive•Diamond•Graphite•Buckminsterfullerene

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.

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.

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.

Carbon Family

Ant (carbon-based organism) holding microchip (probably made of germanium or silicon)

Ant (carbon-based organism) holding microchip (probably made of germanium or silicon)

Nitrogen Family • 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

• 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.

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.

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.

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.

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.

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.