NAMING COVALENT COMPOUNDS
BINARY MOLECULAR COMPOUNDS
Binary molecular compounds are formed from two nonmetals held together by covalent bonds
Elements in binary molecular compounds can combine in different ways. Carbon and Oxygen can combine as CO and CO2
NAMING MOLECULAR COMPOUNDS
Covalent compounds are named differently than ionic compounds
Since covalent compounds can form multiple compounds with each other they can not be named the same as ionic compounds
Nitrogen and oxygen can form N2O, NO, No2, and N2O5. If they were named like ionic compounds they would all be called nitrogen oxide.
USING PREFIXES With covalent
compounds a prefix is used to indicate how many atoms of an element are in a compound.
Often the mono- prefix is omitted, but is used as an emphasis in some cases like carbon monoxide
Number of Atoms
Prefix
1 mono-
2 di-
3 tri-
4 tetra-
5 penta-
6 hexa-
7 hepta-
8 octa-
NAMING MOLECULAR COMPOUNDS
First confirm that both elements are nonmetals
Name the elements in the order listed in the formula
Use prefixes to indicate the number and kind of atoms
The suffix of the second element is –ide
NOnitrogen oxideNO2
nitrogen dioxideN2Odinitrogen monoxideN2O5
Dinitrogen pentoxideCl2O8
Dichlorine octoxide
Number of Atoms
Prefix
1 mono-
2 di-
3 tri-
4 tetra-
5 penta-
6 hexa-
7 hepta-
8 octa-
WRITING BINARY MOLECULAR COMPOUNDS
When writing the formula for a binary molecular compound, use the prefixes in the name to give the numbers of each element in the compound
First write the symbols of the elements involved in the compound
Next add subscripts based on the prefixes
EXAMPLE
Write the formula for silicon carbide The symbol for silicon is Si and the symbol
for carbon is C There are no prefixes, so the formula is SiC
EXAMPLE
Write the formula for carbon dioxide The symbol for carbon is C and the symbol
for oxygen is O The prefix on oxygen is di- which means 2, so
the formula is CO2
PRACTICE
Carbon tetrabromide
Diphosphorus trioxide
Iodine dioxide
CBr4
P2O3
IO2
LAWS OF DEFINATE PROPORTION
The law of definite proportions state that in the sample of any compound, the masses of the elements are always in the same proportions
No matter the size of the sample, the ratio of mass of one compound to another will always be the same
The law of multiple proportions states that whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.
When comparing to compounds with the same elements, the ratio of masses will be of the elements will be in a whole number ratio.
H20 and H202, the ratio of oxygen is 2:1 for the same mass of hydrogen