9.5 – NOTES Alkanes

Naming covalent compounds that are not hydrocarbons determine the name of the first element If there are no subscripts on the symbol, name the element as it is If there is a subscript on the first symbol, put the prefix associated with the number in front of the name 2 – di 3 – tri 4 – tetra 5 – penta 6 – hexa 7 – hepta 8 – octa 9 – nona 10 - deca

Determine the name of the second element Look at the second element in the compound and determine how many atoms of that element are present. Put the prefix associated with the number in front of the element name. The prefixes are the same as the first part, only you now use mono to show that one atom is present 1 – mono 2 – di 3 – tri 4 – tetra 5 – penta 6 – hexa 7 – hepta 8 – octa 9 – nona 10 - deca   Change the ending of the second element to –ide Oxygen becomes oxide, phosphorus becomes phosphide, etc.

Examples N2O5 BF3 CO H2O SBr6 PCl5

Special Compounds: A few compounds do not use this naming system Special Compounds: A few compounds do not use this naming system. Be familiar with these formulas and names CH4 Methane NH3 Ammonia

Modeling Alkanes Two kinds of models Ball and stick models Balls are atoms and sticks are covalent bonds. Useful to show geometry, but bonds are not actually sticks. Ex. CH4

Space-filling model Atoms are in contact with each other, and this model is more accurate Ex. CH4 Tetrahedron Pyramid shaped molecule with a triangle base

Molecular formula Condensed formula Specifies how many of each atom types you have, doesn’t give any idea of molecules shape Ex. CH4, C2H6, C3H8 Condensed formula Show how atoms are arranged in a molecule, not just their number of atoms present More useful Examples:  Structural (Draw here) Condensed CH4 CH3CH3 CH3CH3CH3

Alkanes Simplest hydrocarbon, only has C+H, all single bonds General formula for alkanes is CnH(2n+2), where n = the number of carbons. Prefixes for hydrocarbons 1=meth 2=eth 3 = prop 4=but 5=pent 6 = hex 7=hept 8=oct 9=non 10=dec Naming Alkanes Count the number of carbons present and find the appropriate prefix Put the ending – ane after the prefix

Examples C2H6 Ethane C9H20 Nonane