Naming Molecules and Writing Molecular Formulas

Naming Binary Molecular Compounds

prefixes tell how many atoms of each element are present

still end with -ide

vowel of the prefix is often dropped

omit prefix mono- for the first element

Greek numerical prefixes. 

Number Prefix1 -mono2 -di3 -tri4 -tetra5 -penta6 -hexa7 -hepta8 -octa9 -nona

10 -deca

First to name covalent compounds we need to know some Greek numerical prefixes.  It'd be a good idea to memorize these since they will be useful in many other classes.  

Writing formulas for binary molecular compounds

write the symbol and use prefixes of each element in order write subscripts for that element

carbon monoxide → CO

nitrogen triiodide → NI3

Naming and Writing Formulas for Acids

acids produce hydrogen ions (H+) when dissolved in water

naming

1. ends in –ide → acid begins with hydro- and ends with –ic

H2S would normally be dihydrogen sulfide

→ acid name is hydrosulfuric acid

2. ends in –ite → only say the anion and it ends in –ous

HNO2 would normally be hydrogen nitrate

→ acid name is nitric acid

3. ends in –ate → only say the anion and it ends in –ic

HMnO4 would normally be hydrogen permanganate

→ acid name is permanganic acid

Writing formulas for acids

reverse the rules for writing names of acids (remember, acids start with hydrogen even if not in the name)

hydrobromic acid → must be hydrogen ion (H1+) and a bromide ion (Br1-). Therefore, is HBr

phosphorous acid → must be hydrogen (H) and phosphite (PO3)3-. Therefore, is H3PO3

Naming and Writing Formulas for Bases an ionic compound that produces hydroxide

ions (OH-) when dissolved in water

Naming

bases are ionic compounds so name like any other ionic compound– just say it!

NaOH is sodium hydroxide

KOH is potassium hydroxide

Formulas

find ionic charges and criss-cross them

aluminum hydroxide contains the ions Al3+ and OH1- and therefore Al(OH)3