Transcript Molecular Compounds and Nomenclature

2.4 Molecular Nomenclature
Molecular compounds are made of two or
more non-metals which share pairs of
electrons to form bonds.
 Each pair of shared electrons is called a
covalent bond.
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The names of molecular compounds often
contain prefixes.
 The prefixes are used to count the number
of atoms in the molecule.
 This is important as molecular compounds
containing two elements can have different
combinations of atoms which have different
properties.
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# of
atoms
1
2
3
4
5
6
7
8
9
10
Prefix
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
Naming Binary Molecular
Compounds: IUPAC
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Write down the name of the first element.
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If there is more than one atom of this element
attach a Greek prefix (if there is only one atom do
not attach the prefix)
Attach a Greek prefix (relating to the number of
atoms) to the second element’s name and add
-ide.
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Example: name N2O4
Two nitrogen atoms; therefore, dinitrogen
 Four oxygen atoms; therefore, tetraoxide
 Final answer: dinitrogen tetraoxide
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Example: name BrCl
One bromine atom; therefore, bromine
 One chlorine atom; therefore, monochloride
 Final answer: bromine monochloride
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Writing Formulae for Binary
Molecular Compounds
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Write the symbol for the first element and
use subscripts to show the number of atoms
of that element based on its prefix
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Remember that no prefix means one atom
Write the symbol for the second element and
use subscripts to show the number of atoms
of that element based on its prefix
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e.g.: write the formula for dinitrogen pentoxide
di- = 2, therefore, we have two nitrogen atoms: N2
 penta- = 5, so, we have five oxygen atoms: O5
 Final answer: N2O5
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e.g.: write the formula for carbon monoxide
No prefix means we have one carbon atom: C
 mono- = 1, so, we have one oxygen atom: O
 Final answer: CO
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Diatomic Elements
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Some elements form covalent bonds with
themselves to form diatomic (two atoms)
molecules
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H2, O2, F2, Br2, I2, N2, and Cl2
When naming no prefix or suffix is used
 You must know which elements form
diatomic molecules
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The mnemonic device HOFBrINCl (hoff-brincle)
can help you remember
Homework
Read pp. 79 – 80
 Complete Worksheet
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