Periods Periodic trends are established as you go across a row. What happens to the elements as you go across the row?

Metal vs. Non-metal Periodic trends are established as you go across a row. What happens to the elements as you go across the row?

Groups or Families These elements are closely related because they have the same number of valence electrons. What does that mean?

Alkali Metals (Group 1) These elements are highly reactive metals. WHY??? Lithium, Sodium, Potassium, Rubidium, Cesium, & Francium all have 1 valence e-. ALL are S 1

What are valence electrons? Electrons in the outermost energy level. They determine an element’s chemical properties. They are involved in bonding.

Electron/Lewis Dot Structures Symbols of atoms with dots to represent the valence-shell electrons H  He:            Li  Be   B   C   N   O  : F  : Ne :                    Na  Mg   Al   Si   P   S  : Cl  : Ar :        

Electrons in Energy Levels 1 st energy level = 2 electrons 2 nd energy level through the rest = 8 electrons All energy levels seek a full valence so they are “stable”.

Octect Rule Elements want eight (8) electrons in the outer shell in order to become stable. Elements “want” their outer shell filled. They either gain or lose e- in order to accomplish this. They get the same e- configuration as previous NOBLE GAS or next NOBLE GAS

Sodium (Na) Valence shell is not full. It takes less energy to give away 1 electron than “steal” 7 more. Tend to Lose 1 e- +1 charge

Alkaline Earth Metals (Group 2) Be, Mg, Ca, Sr, Ba, Ra How many valence electrons do they have? Are they still considered “reactive”? WHY? All are ALL are S 2 Are they more/less reactive than Group 1? LESS Lose 2 e- (+2) charge

Magnesium (Mg) What kind of an ion will it form? WHY??? It is easier (less energy) to give away 2 electrons than “steal” 6 from somewhere else. +2 charge

Other Families Group 13 “Boron Family” = P 1 = 3 valence e- (S 2 & P 1 ) (+3) charge Group 14 “Carbon Family” = P 2 = 4 valence e- (S 2 & P 2 ) (+4,-4 charge) Group 15 “Nitrogen Family” = P 3 = 5 valence e- (S 2 & P 3 ) (-3 charge) Group 16 “Oxygen Family” = P 4 = 6 valence e- (S 2 & P 4 ) (-2 charge) Group 17 “Halogens” = P 5 = 7 valence e- (S 2 & P 5 ) (-1 charge) Group 18 “Noble Gases” = P 5 = 8 valence e- (S 2 & P 6 ) (0 charge)

The Halogens (Group 7) Fluorine, Chlorine, Bromine, Iodine, Astatine. Have 7 valence electrons (very reactive), they need 1 more to have a full valence! gain 1 e- (-1 charge)

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

The Noble Gases (Group 8) Very stable and “unreactive” (inert). All have 8 valence e- except for Helium. Why is Helium still considered a noble gas? 1s2 shell is filled (inner shell)

What ion would Aluminum make? How do you know?

Al +3

Determine the charges

BONDING Elements BOND (join to make COMPOUNDS) in order to fill their OUTER SHELLS.

Ionization Cation has a POSITIVE net charge. What kind of elements form Cations? Group 1,2 & 3 do! Anion has a NEGATIVE net charge. What kind of elements form Anions? Group 5,6 & 7 do!

How can we represent these types of molecules??? Electron Dot Diagram A “model” chemists use represent the electron sharing in covalently bonded molecules. Example: Hydrogen (H), has 1 valence electron. H·

The dots in an Electron Dot Diagram are placed in a specific order: E

Try some on your own: Na, Mg, Al, C, N, and Cl

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons H  He:            Li  Be   B   C   N   O  : F  : Ne :                    Na  Mg   Al   Si   P   S  : Cl  : Ar :        