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How can I write binary ionic formulas?

Answer 1

Use the criss-cross method.

The criss-cross method involves taking the size of the charge of the cation and making it the subscript of the anion, and taking the size of the charge of the anion and making it the subscript of the cation.

Example 1.

Sodium chloride

#"Na"^(+) + "Cl"^(1-)##rarr##"Na"_cancel1"Cl"_cancel1"##rarr##"NaCl"#

When the subscripts are the same they cancel to #1#, which is understood, but not written.

Example 2.

Barium fluoride

#"Ba"^(2+)"+ F"^(1-)"##rarr##"Ba"_1"F"_2##rarr##"BaF"_2"#

Example 3.

Aluminum oxide

#"Al"^(3+)"+ O"^(2-)##rarr##"Al"_2"O"_3"#

Example 4.

Copper (II) oxide

#"Cu"^(2+)"+ O"^(2)##rarr##"Cu"_cancel2"O"_cancel2##rarr##"CuO"#

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Answer 2

Ellie Andrews

In order to balance the charges, write the symbols for the cation and anion in that order, indicating the charges with subscripts.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.