Ionic Naming & Formula Writing
Covalent Naming & Formula Writing
Ionic Naming:
Formula will always start with a metal (cation)
Formula will sometimes have a polyatomic ion
(look at your reference sheet)
Always name the metal first
o Parent name on the periodic table
o If it’s a transition metal, you will have to
figure out the charge (these are the
metals in the middle of the periodic table.
o Transition metals ALWAYS NEED A
CHARGE in parentheses between the
cation and anion.
o Base the charge on the anion’s charge and
quantity.
Name the non-metal/polyatomic ion next
o Non-metal (anion): -ide suffix
o Polyatomic ion: name on sheet
Formula name will always be:
o Metal + non-metal/polyatomic ion
IGNORE THE SUBSCRIPTS FOR NAMING
Name will always be only TWO WORDS
Example:
o Fe2O3
o First element: iron (transition metal)
Need charge: Based on oxygen’s
charge (-2)
o Second element: oxygen; change to
oxIDE
o Name: Iron (II) oxide
Covalent Naming:
Formula given will start with a nonmetal (anion),
followed by a nonmetal
o Right hand side above the staircase
You need prefixes for the amount of atoms you
have of each element
First nonmetal:
o Parent atom on the periodic table
o Never start with “mono” prefix if there is
only one atom
o If more than one atom of first nonmetal,
give prefix
Second nonmetal:
o Prefix + parent atom root, and suffix –ide
o Second nonmetal ALWAYS gets a prefix,
even if there is only one atom
NO POLYATOMIC IONS
You will also need to memorize the diatomic
molecules on the periodic table (there are 7 total)
o N, O, F, Cl, Br, I, H
o They are written with a subscript of 2
ALWAYS when naming
Example:
o SO2
o S = sulfur (nonmetal), only one atom, no
prefix needed
o O2 = dioxide, there is a subscript of 2,
need prefix for oxygen.
o Name: Sulfur dioxide
Ionic Formula Writing:
First name given will be a metal (from left hand
side of periodic table all the way over to under the
staircase on the right hand side)
o Periodic metal (parent name)
o Transition metal (will have a CHARGE in
parenthesis between cation/anion)
Second name will be a non-metal (right hand
side of the periodic table, above the staircase) or
polyatomic ion name.
o Generally:
o –ide: non-metal
o –ate or –ite polyatomic
o Huge exception: OH or hydroxide. This is
a polyatomic, not H or hydride
Write your symbols, then get their charges.
CRISS CROSS FOR FORMULA
o If charges are exact opposites (i.e. +2 and
-2) they cancel; no need for crisscrossing.
Charges become subscripts for opposite atom,
unless they cancel out
Example:
o Magnesium oxide
o Magnesium: Mg (+2)
o Oxide: O (oxygen) (-2)
o Charges cancel, so no crisscross needed
o Formula: MgO
Covalent Formula Writing:
Name given will have prefixes (always on
second nonmetal) and will start with a nonmetal
name
Both elements will be NONMETALS
Use prefix chart to figure out the quantity of atoms
in the formula
Prefixes become SUBSCRIPTS for atom named.
o Example: nitrogen dioxide
o Nitrogen = no prefix, so just one atom
o Di = two
o Oxide = oxygen
o Translation: 1 nitrogen atom and 2
oxygen atoms
o Written: NO2