1 of 20

formulae of ionic compounds

2 of 20

Types of ions

  • Monatomic ion
    • ion with one atom
      • Mg2+ magnesium ion
      • Cl- chloride ion
  • Polyatomic ion
    • ion with more than one atom
      • NH4+ ammonium
      • NO3- nitrate

3 of 20

Ionic Compound Marriage

Metals are like men

Nonmetals are like woman

Typically who changes their last name?

4 of 20

Naming Ca”t”ions

  • Monatomic cation name stays the same
    • Sodium, Na goes to sodium ion, Na+
    • Calcium, Ca goes to calcium ion, Ca 2+
    • Polyatomic cation - look up in chart
    • NH4+ ammonium

​

​

5 of 20

Naming Anions

  • The name changes in a monatomic anion
  • The ending for a monatomic anion is ______ide

(like a bride changes her last name)

    • chlorine, Cl goes to chloride ion, Cl-
    • Fluorine, F goes to fluoride ion, F-

​

  • Polyatomic anion look up in chart
    • OH- hydroxide
    • SO42- sulfate

6 of 20

7 of 20

Question Time

Given the neutral atom, give the charge and name of the monatomic ion that will form. (Look at periodic table group numbers for help.)

  1. Na
  2. Cl
  3. Mg
  4. S
  5. P

Na+

sodium cation

Cl-

chloride anion

Mg2+

magnesium cation

S2-

sulfide anion

P3-

phosphide anion

8 of 20

Name the following polyatomic ions.

(use your chart!)

  1. NH4+
  2. OH−
  3. SO32−
  4. SO42−
  5. CN−

ammonium cation

sulfite anion

sulfate anion

cyanide anion

hydroxide anion

9 of 20

Naming ionic compounds

  • Name the cation first and then the anion second (+ then -)
  • Example: CsF
    • Monatomic cations use the element name
      • Cs+ = cesium
    • Monatomic anions – change the ending to ide
      • F - = fluoride

cesium fluoride

10 of 20

Will these form an Ionic Compound? �If so what will the compound name be?

  1. Mg Al
  2. Al S
  3. Mg O
  4. Na N
  5. C S

No

Yes

aluminum sulfide

Yes

magnesium oxide

Yes

sodium nitride

No

two non-metals

two metals

11 of 20

Formula Unit�

  • Formula Unit—the smallest whole number ratio of ions in a compound
  • NaCl versus Na2Cl2

​

  • Correct: Sodium Chloride NaCl

​

​

12 of 20

What will the formula be?

  • In ionic compounds, we must balance charges to form a neutral compound

​

  • To do that, we “crisscross the charges”
  • Always reduce to get the formula unit

​

Ca + N

Ca2+ +

N3-

Ca3

N2

Both have a total charge of 6 (3 Ca2+ = +6; 2 N3- = -6)

13 of 20

Practice

Given the following elements, predict the formula. (hint first identify the ion charge)

  1. K, Br
  2. Ca, Cl
  3. Li, S
  4. Mg, N
  5. Ba, P

​

​

14 of 20

Formula Unit with Polyatomic ions

  • Sometimes you will need to use more than one polyatomic ion to balance a charge.
  • If so, you need to put it in parenthesis (like a package) and use a subscript for the multiple number

Ex: Mg2+ and NO3-

These charges do not balance so we must crisscross them

Mg1(NO3)2 (we don’t need the 1)

Mg (NO3)2

15 of 20

Transition Metal Ions

  • Metals form cations
  • Some transition metals only have one ionic charge
    • Silver (Ag+), Cadmium (Cd2+), Zinc (Zn2+)
  • Some transition metals can take on more than one charge.
    • Copper (Cu+, Cu2+)
  • Charge is determined from the number of electrons lost

16 of 20

Naming Transition Metal Ions

  • If a transition metal has more than one charge, the charge is written as a Roman numeral in parenthesis
  • Some metals need a middle name
  • Fe (iron) has more than one charge: 2+ and 3+

​

    • Fe2+ iron(II)
    • Fe3+ iron(III)
  • If the transition metal only has one charge, no Roman numeral is needed

17 of 20

Naming Ionic Compounds with Transition Metals

    • First find the charges of the ions

​

    • Then name the cation followed by the anion
      • Iron(III) oxide

​

    • Try this one: Fe3P2
      • the charge on iron is a 2+
      • iron(II) phosphide

Given: Fe2O3

18 of 20

Question Time

Identify the charge on the transition metal:

    • copper (II) nitrate
    • gold (I) chromate

Name the compound:

    • FeO
    • Zn(OH)2
    • CoPO4

​

2+

1+

iron (II) oxide

zinc hydroxide

cobalt (III) phosphate

19 of 20

Related Search Terms

  • formulae of ionic compounds
  • formula for ionic compounds
  • formulas for ionic compounds
  • formula of ionic compounds
  • formula ionic compounds
  • formula of an ionic compound
  • write formulas for ionic compounds
  • formula for ionic compound
  • how to write formula for ionic compounds
  • writing the formula for ionic compounds
  • how to write the formula of an ionic compound

​

  • https://goo.gl/cev35Z

20 of 20