1. Ionic Compounds

2. An ion is an atom that has gained or lost an electron
What is an ion?
An ion is an atom that has gained or lost an electron
Cation – lost electron – name stays the same – sodium ion
Anion – gained an electron – adds –ide to the end - chloride

3. How many electrons does an atom start with?
Atomic number:
Number of protons
Number of electrons

4. How do you know if an atom will lose or gain?
Metals lose electrons until they reach the electron configuration of a noble gas
Nonmetals gain electrons until they reach electron configuration of a noble gas

6. octet Sodium atom Sodium ion Na+ 1s2 2s2 2p6 Na 1s2 2s2 2p6 3s1
(Same electron configuration as Neon)

7. Written as a superscript after the element symbol
Oxidation numbers
Oxidation numbers are used to keep track of how many electrons are lost or gained
Written as a superscript after the element symbol
+ indicates electrons lost (less electrons)
- indicates electrons gained (more electrons)
Ex: Na+1
Ex: Cl-1

9. Properties of ionic compounds
Brittle solids
High melting points
Electronically neutral compounds
Soluble in water
When dissolved in water, they are known as electrolytes
Ionic compounds are known as salts

10. Electrons transfer from one atom to another
Ionic bonds
Formed between a Cation (+)(“giver”) or (metal) and an anion(-) (“taker”) or (nonmetal)
Electrons transfer from one atom to another

11. 2 types of ionic compounds
Binary – has just two elements with total charge equaling zero
Ex. NaCl
Ternary – involve three (or more) elements, usually forming a polyatomic ion group

12. Formula for binary ionic compound
Ex: magnesium chloride
Magnesium ion has a +2 charge
Chloride ion has a -1 charge
So we need 2 Cl for every 1 Mg
MgCl2
Ratio of Mg to Cl is 1:2

13. Write symbol for + ion (metal) and its charge.
Criss cross method
Write symbol for + ion (metal) and its charge.
Write symbol for – ion (nonmetal) and its charge
Reduce to lowest terms
Criss-cross
(If subscript is a 1, no need to put it in formula)

14. Criss cross method example
Sodium oxide
Sodium and oxygen
Na O
Na1+ O2-
= Na2O

15. A formula unit smallest part of an ionic compound
Ex. NaCl is 1 formula unit of table salt.
3NaCl is 3 formula units of table salt

16. Stock name and classical name
transition metals
Stock name and classical name
Stock – preferred naming system, uses Roman numerals in parentheses to placed after the name of the element to indicated the numerical value of the charge ex: Fe2+ would be iron(II)
Classical- older method uses root word with different suffix -ic and – ous
-ic is used for the higher of the two ionic charges
-ous is used for the smaller of the two charges

17. List of Common metal ions with more than one ionic charge
Copper (I)
Copper (II)
Iron (II)
Iron (III)
Mercury (I) - Hg22+ diatomic elemental ion
Mercury (II) – Hg2+
Cobalt (II)
Cobalt (III)
Lead (II)
Lead (IV)
Tin (II)
Tin (IV)
Chromium (II)
Chromium (IV)
Manganese (II)
Manganese (III)

18. Summary
How do you know what the charge is? Practice grasshoppers, just practice
Cu 1+ and 2+
Fe, Mn, Cr, Co all 2+ and 3+
Pb and Sn are 2+ and 4+
Hg2 2+ mercury(I)
Hg2+ mercury(II)

19. Other exceptions
Group 4A: usually form ions with 4+ charge. Sn and Pb also produce ions with 2+ charge- may only lose 2 electrons from p-sublevel
Ag is always 1+
Cd is always 2+
Zn is always 2+

20. Ternary ionic compounds
Involve polyatomic ions:
Two or more atoms that are bound together by predominantly covalent bonds, but have gained or lost an electron in order to become more stable
Act as a whole when forming an ionic compound

21. Chromate CrO4 2- Acetate C2H3O21- Permangenate MnO41- Hydroxide OH1-
Polyatomic ions
Sulfate SO42-
Phosphate PO43-
Carbonate CO32-
Nitrate NO31-
Bromate BrO31-
Chlorate ClO31-
Chromate CrO4 2-
Acetate C2H3O21-
Permangenate MnO41-
Hydroxide OH1-
Ammonium NH41+

22. Writing Ternary ionic compound formulas
Potassium sulfate K+1 SO42- K2SO4

23. Mg(OH)2 Ex. Magnesium and hydroxide Mg and (OH) Mg 2+ and (OH)1-
Use criss-cross method
Mg(OH)2
*If there is more than one polyatomic ion group, you must put it in parentheses.

24. Calcium sulfate
Potassium phosphate
Ammonium sulfite
Ammonium hydroxide

25. Naming Ionic Compounds with Polyatomic Ion Groups
Same rules as binary ionic compounds, but if it has a Polyatomic Ion Group, use group name