NTI Day 3
Writing Ionic Formulas
An ionic compound is a chemical compound comprising ions held together by electrostatic
forces termed ionic bonding. The compound is neutral overall, but consists of positively charged
ions called cations and negatively charged ions called anions. These can be simple ions such as
the sodium (Na+) and chloride(Cl−) in sodium chloride, NaCl, or polyatomic species such as
the ammonium (NH4+) and carbonate (CO32−) ions in ammonium carbonate (NH4)2CO3.
Ionic compounds form when elements, or polyatomic ions, have a large difference in
electronegativities. Electrons from one species is transferred to another, resulting in oppositely
charged ions that attract to each other.
Writing Ionic Formula Notes:
1.
Write first element and its oxidation number (charge); if first element is a transition
metal, the Roman numeral will indicate the charge.
2.
Write second element/group of elements and its oxidation number.
3.
If oxidation #s add to zero, cancel them; if not, switch
For more examples of how to write formulas of binary ionic compounds which are composed of a
metal and a nonmetal, pull your work from your notes. Additional examples can be viewed in this
tutorial.
https://www.youtube.com/watch?v=URc75hoKGLY
For more examples of how to write formulas of ionic compounds with transition metals, pull your
work from your notes. Additional examples can be viewed in this tutorial.
https://www.youtube.com/watch?v=H4nfE8gRX7Q
For more examples of how to write formulas of ionic compounds with polyatomic ions, pull your
work from your notes. Additional examples can be viewed in this tutorial.
https://www.youtube.com/watch?v=p9iQ5Qn42DM
Multiple Choice
Identify the choice that best completes the statement or answers the question.
1. What is the formula for lead (IV) oxide?
(a) PbO2
(b) PbO
(c) Pb2O
(d) Pb2O2
2. What is the formula for iron (III) oxide?
(a) FeO
(b) FeO3
(c) Fe2O
(d) Fe2O3
NTI Day 3
3. What is the formula for phosporous sulfide?
(a) PS
(b) P4S3
(c) P2S3
(d) P4S2
4. What is the formula for iron (II) sulfide?
(a) FeS
(b) Fe2S3
(c) Fe2S
(d) Fe2S3
5. What is the formula for iron (II) fluoride?
(a) FeF
(b) Fe2F
(c) FeF2
(d) Fe2F
6. What is the formula for lithium nitrate?
(a) Li2NO3
(b) LiNO3
(c) Li(NO3)2
(d) Li3NO
7. What is the formula for potassium hydroxide?
(a) K2H
(b) K(OH)2
(c) KH
(d) KOH
8. What is the formula for ammonium bromide?
(a) NHBr4
(b) NH4Br2
(c) (NH4)2Br
(d) NH4Br
9. What is the formula for beryllium nitride?
(a) BeNO3
(b) Be2NO3
(c) Be3N2
(d) Be3N
10. What is the formula for potassium carbonate?
(a) K3CO
(b) K2(CO)3
(c) K2CO3
(d) KCO3
11. What is the formula for strontium iodide?
(a) SrI
(b) Sr2I3
(c) SrI3
(d) SrI2
12. What is the formula for magnesium phosphate?
(a) Mg3(PO4)2
(b) MgPO4
(c) Mg(PO)4
(d) Mg2(PO4)3
13. What is the formula for hydrogen cyanide?
(a) HCN2
(b) H2CN
(c) HCN
(d) H3CN2
14. What is the formula for boron fluoride?
(a) BF2
(b) BF3
(c) BF
(d) B2F3
15. What is the formula for aluminum oxide?
(a) AlO
(b) AlO3
(c) Al2O3
(d) Al3O2