Criss-cross notes

Criss-Cross MethodCriss-cross is a _________ to help you find chemical __________ when you _________ atoms.

shortcut

formulascombine

**Formulas contain both the ________ in a compound and the _______ of that element.elementsamount

How Many?

NaCl = 1 sodium1 chlorine

MgCl2 =

1 magnesium2 chlorines

This number is called a ________subscript

It tells you the _______ of the atom ________ in front of it!

amountdirectly

First – you need to determine the _________ number for each atom.oxidation

To get started…

You can find them in the ______- ______ corner on the Periodic Table.

upperright

OxidationOxidation numbers are the _____ that will form when atoms _________ their _________ shells.

ions

complete valence

Cl Cl-1

Oxidation number

More than one?Many atoms have more than one oxidation state!

We will use the ______ one listed!

first

(This is the one most _________ formed in nature!)

commonly

Find the correct formula for a compound!!•Use the oxidation #’s•Put the _______ one first

H+1 + O-

2 H2O

positive

What just happened?By switching the numbers, the _________ number of one atom becomes the _________ for the other!

oxidation subscript

This also makes sure that we end up with a _______ compound – all the ________ of the ions add up to ______.

neutralcharges

zero

Stuff to remember…‘Ones’ are ________. (Think Math!)

invisible

If both of your ions have the _____ oxidation number -- ______ to the ______ common number!

samereduce lowest

It will make more sense after examples…

Ca + Br CaBr2+2 -1

Mg + Cl MgCl2+2 -1

Sr + O Sr2O2+2 -2 SrO

Don’t forget the rules for naming:1. ______ always goes first!Metal

2. ________ goes second – and ends in _____!

Nonmetal“-ide”