Mastering Ionic Compounds Through Formula Creation

The video tutorial explains how to write chemical formulas using the crisscross method. It starts with a simple example of combining sodium and chloride ions to form NaCl. The tutorial then progresses to more complex examples involving polyatomic ions, such as sulfate and phosphate, demonstrating the importance of using parentheses to maintain the integrity of polyatomic ions. The final example combines two polyatomic ions, NH4 and PO4, to illustrate the method further. Throughout, the tutorial emphasizes the importance of not altering the subscripts within polyatomic ions.

What is the charge of Na+ in the given example?

• 0

• +2

• +1

• -1

When combining Na+ and Cl-, what is the correct formula?

• NaCl2

• Na2Cl

• NaCl

• Na2Cl2

What is the purpose of the crisscross method?

• To predict the state of matter

• To determine the color of a compound

• To find the molecular weight

• To balance charges in a chemical formula

Why are parentheses used around polyatomic ions like sulfate?

• To show they are gases

• To prevent altering the internal subscript

• To indicate a solid state

• To separate them from other ions

What is the charge of sulfate (SO4) in the example?

• +2

• +1

• -2

• -1

What is the correct formula for combining Na+ and SO4-2?

• NaSO4

• Na2SO3

• NaSO3

• Na2SO4

In the example with NH4+ and PO4-3, what is the charge of NH4+?

• +1

• -1

• +2

• -3

What is the correct formula for combining NH4+ and PO4-3?

• (NH4)3(PO4)

• (NH4)3PO4

• NH4(PO4)3

• NH4PO4

How many NH4 ions are present in the final formula with PO4-3?

• 1

• 2

• 3

• 4

What does the final formula (NH4)3PO4 indicate about the number of PO4 ions?

• 2

• 3

• 1

• 4