Inside the Atom Periodic Table Covalent Bonding

Electron Shells Contain all electrons at approx. same energy and distance out. Shell Number designation Electron capacity (2n*n) 1 st nd 28 3 rd th th 550

Valence Electrons Electrons in outer shell –Farthest out –Most loosely held Most likely to be involved in a chemical reaction

Periodic Law Attributed to Mendeleev – 1869 Similar properties regular intervals (periods) Based on experimental results (laws) Didn’t know why (theory) until electron orbits or shells were discovered

Representative Elements

Halogens

Valence Electrons Equal to the number of the column for representative elements –So all elements in a column have same # of valence electrons (representative) –Valence electrons determine chemical behavior –Example Ca and Sr

Lewis or Electron Dot Structure Number of dots = number of valence electrons = number of column.

Octet Rule of Bonding All but smallest atoms want to have 8 valence electrons Or all atoms want to be like the closest Noble Gas –Lose electrons –Gain electrons –Share electrons – Covalent Bonding Ionic Bonding

Covalent Bonding Sharing electrons instead of transferring – H + H → H H – Cl + Cl → Cl Cl – H + O + H → H O H or H – O – H H H – 4H + C → H C H or H – C – H H H Nobel gas configuration

Water

Covalent Bonding Number of bonds an atom wants to form? –Equal to number of electrons it is missing to be like a noble gas How many O’s will react with C ? How many F’s will react with N ?

Multiple Covalent Bonds Single bond – share one pair of electrons Double bond – share two pair Triple bond – share three pair All but group VIIA and H can double bond Group IVA & VA can triple bond –Mostly C, N, Si, P

Naming Binary Covalent Compounds

Shapes of Compounds You will get a good feel for shapes in lab 5

H8 – C3 16, 18, 19, , 27, 28, 31, 32, 55, 56, 60, 62, 64, 80