Representative groups

Representative groupsValence Electrons electron that is in the highest occupied energy level electrons in the last energy level

elements in a group have similar properties because they have the same number of valence electrons.

Valence ElectronsA groups on table are numbered from 1 through 8group # based on # of valence electrons

Valence electrons play a key role in chemical reactions. Properties vary across a period because the number of valence electrons increases from left to right.

Alkali Metals Group 1A one valence electron extremely reactive found in nature only in compounds produce hydrogen gas when in contact with water larger number of energy levels means greater reactivity

Alkali Metals-reactionsSodium reacts violently with water and releases enough energy to ignite the hydrogen gas that is produced.

Sodium and potassium are stored under oil to keep them from reacting with the oxygen and water vapor in air.

Cesium is so reactive that it is usually stored in a sealed glass tube containing argon gas. Alkaline Earth MetalsGroup 2A2 valence electronsLess metallic than alkali metalsharder than metals in alkali metalsm.p. of magnesium is 650Cm.p. of sodium 98C.

Alkaline Earth metals- ReactionsCalcium, strontium, and barium react easily with cold water. Magnesium will react with hot water but not cold water.No reaction occurs when beryllium is added to water.

Alkaline Earth MetalsMagnesiumMagnesium plays a key role in photosynthesis. The compound at the center of this process is chlorophyll, and at the center of chlorophyll is a magnesium atom. A mixture of magnesium and other metals can be as strong as steel, but much lighter. The frames of bicycles and backpacks often contain magnesium.

Alkaline Earth MetalsCalciumCalcium carbonatea compound of calcium, carbon, and oxygenis the main ingredient in chalk, limestone, and coral.Your toothpaste may contain the compound calcium carbonate because this hard substance can polish your teeth. Magnesium and calcium have essential biological functions, and they provide materials used in construction and transportation.

Chlorophyll molecules in spinach contain magnesium. An oyster shell and a pearl are both made from calcium carbonate. A plaster cast contains the compound calcium sulfate. The Alkaline Earth Metals

Spinach plantOyster shell with pearlPlaster cast10Boron Family Group 3A contains 3 valence electrons the metalloid boron aluminum, gallium, indium, and thallium are metals aluminum most abundant metal in the earths crust

Carbon FamilyGroup 4A 4 valence electrons Elements bond to metals/nonmetals or elements in own family- oil (carbon) = $$$ contains 1 nonmetal (carbon)2 metalloids (silicon and germanium)2 metals (tin and lead)

Nitrogen FamilyGroup 5A contains 2 nonmetals (nitrogen and phosphorus) 2 metalloids (arsenic and antimony)1 metal (bismuth) elements contain 5 valence electrons

Nitrogen FamilyNitrogen is a nonmetal gas Nitrogen forms diatomic moleculesIn pure form, 2 atoms bond together Oxygen FamilyGroup 6A contains 3 nonmetals2 metalloids6 valence electrons oxygen forms a diatomic molecule oxygen the most abundant element in the earths crust 2nd most abundant element in the atmosphere combines with almost every element on table

Oxygen FamilyComplex forms of life need oxygen to stay alive because oxygen is used to release the energy stored in food. Ozone is another form of the element oxygen. At upper levels of the atmosphere, ozone absorbs harmful radiation emitted by the sun.Sulfur was one of the first elements to be discovered because it is found in large natural deposits.

Halogens Group 7A are called halogens. 7 valence electrons contains an element in each phase At room temp, chlorine (gas), bromine (liquid), & iodine (solid) 1st four elements form diatomic molecules Very reactive

HalogensHalogens react easily with most metals. This photograph shows chlorine reacting with steel wool

Noble Gases Group 8A are called noble gases Helium has 2 valence electrons (only 1 level) Each of the other noble gases has an octet (8 electrons)colorless and odorless and extremely unreactive.

Noble GasesWhen electric current passes through noble gases, they emit different colors. Helium emits pinkneon emits orange-redargon emits lavenderkrypton emits whitexenon emits blue.