Writing Chemical Formulas Notes

Name the following ionic compound: BeCl₂

• beryllium chlorine
• beryllium II chloride
• beryllium chloride
• beryllium dichloride

Answer explanation

This is an Ionic Formula . You name the metal first and then the metal with an -ide ending. Roman Numerals are not needed because the metal is not a transition metal. Prefixes are not used because this is not covalent.

What is the correct formula for the compound, lithium oxide?

• LiO
• Li₂O
• LiO₂
• Li₂O₂

Answer explanation

This is Ionic. Find the charge of the metal, find the charge of the non-metal and crisscross the charges to find the subscripts.

What is the formula for manganese(III) oxide?

• MgO
• Mg₂O₃
• MnO
• Mn₂O₃

Answer explanation

Ionic. The metal is a transition metal. The roman numeral tells you the CHARGE of the metal. Determine the charge of the nonmetal and cross the charges to write the formula.

The formula of calcium phosphate is 

• CaPO₄
• Ca₂(PO₄)₃
• Ca₃PO₄
• Ca₃(PO₄)₂

Answer explanation

Ionic with a Polyatomic. Determine the Charge of the Metal. Use the Polyatomic Reference Sheet to find Phosphate formula and charge. Cross the charges and write the formula. Use Parenthesis ( ) to enclose the polyatomic group. The subscript that you cross down goes on the outside of the parenthesis.

What is the name of Al(NO₃)₃?

• Aluminum trinitrate
• Monoaluminum nitrate
• Aluminum (III) nitrate
• Aluminum Nitrate

Answer explanation

Ionic. Name the metal and then name the polyatomic ion. You do not change the ending of the polyatomic group, it is named just the way it appears on the list.

Name the following ionic compound: Cr(NO₂)₃

• chromium nitrite
• chromium nitride
• chromium III nitride
• chromium III nitrite

Answer explanation

Ionic with a transition metal. You need to determine the charge of the metal because that will be the roman numeral you use between the name of the metal and polyatomic. Cross the subscripts back up to determine the charge. Write the metal first followed by the roman numeral and then the polyatomic.

What is the name of N₂O₃

• Nitrogen trioxide
• Dinitrogen oxide
• Dinitrogen trioxide
• Nitrogen oxide

Answer explanation

Covalent. Use prefixes to write the name. look at the subscript, determine the prefix, write the prefix followed by the element name, then do the same with the second element but end it with the -ide ending.

What is the chemical formula for Tetrasulfur pentoxide?

• SO
• S₄O
• S₄O₅
• S₅O₄

Answer explanation

Covalent. To write the formula, look at the prefix, this becomes the subscript for that element. Write the Symbol of the first element then the prefix as the subscript, repeat for the 2nd element.

What is the name of C₃Cl₈ ?

• Carbon octachloride
• Tricarbon octachloride
• Carbon trichloride
• Octacarbon trichloride

Answer explanation

Covalent. Use prefixes to write the name. look at the subscript, determine the prefix, write the prefix followed by the element name, then do the same with the second element but end it with the -ide ending.

What is the name of Br₆F₁₀ ?

• Bromium fluoride

• Hexabromine fluoride

• Bromium decafluoride

• Hexabromine decafluoride

Answer explanation

Covalent. Use prefixes to write the name. look at the subscript, determine the prefix, write the prefix followed by the element name, then do the same with the second element but end it with the -ide ending.