Mastering Ionic Compounds Through The Criss-Cross Method

Dr. B introduces the criss-cross method for writing formulas of ionic compounds. The video covers examples including calcium nitride, calcium fluoride, calcium sulfate, aluminum sulfate, and iron(III) oxide, demonstrating how to balance charges and write correct formulas. The video concludes with a covalent compound example, carbon dioxide, highlighting the use of prefixes instead of charges.

What is the criss-cross method primarily used for?

• Writing formulas for ionic compounds

• Balancing chemical equations

• Calculating molar mass

• Determining molecular shapes

What is the correct formula for calcium nitride using the criss-cross method?

• Ca2N3

• Ca3N2

• CaN

• CaN2

When using the criss-cross method, what is the charge of calcium in calcium fluoride?

• 3+

• 2+

• 0

• 1+

What is the formula for calcium fluoride?

• CaF

• CaF2

• Ca2F

• Ca2F3

What is the charge of the sulfate ion in calcium sulfate?

• 3-

• 1-

• 2-

• 4-

How many sulfate ions are needed to balance the charge in aluminum sulfate?

• 4

• 3

• 2

• 1

What is the correct formula for aluminum sulfate?

• Al(SO4)2

• AlSO4

• Al2(SO4)3

• Al3(SO4)2

What is the charge of iron in iron(III) oxide?

• 4+

• 3+

• 2+

• 1+

What is the formula for iron(III) oxide?

• Fe3O2

• FeO3

• Fe2O3

• FeO

What does the prefix 'di' in carbon dioxide indicate?

• Four oxygen atoms

• Three oxygen atoms

• Two oxygen atoms

• One oxygen atom