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