Naming Compounds and Writing Formulas

1. Naming Compounds and Writing Formulas

2. Chemical Formulas • Shows the kind and number of atoms in the smallest piece of a substance. • Molecular Formula – number and kinds of atoms in a molecule Ex: CO2

3. Formula Unit • The smallest whole number ratio of atoms in an ionic compound.

4. Systemic Naming • A compound is made of 2 or more elements. • There are too many compounds to remember the names of them all. • The name should tell us how many and what type of atoms.

5. Anion • A negative ion • Has gained electrons • Nonmetals • Charge is written as a superscript on the right F-1 Has gained one electron O-2 Has gained two electrons

6. Cations • Positive ions • Formed by losing electrons so it now has more protons than electrons • Metals K+1 Has lost one electron Ca+2 Has lost two electrons

7. Charges on ions • You can tell the charge of the ion by its location on the periodic table. • Elements in the same group have the same charge when they are ions.

8. +1 +2 +3 -3 -2 -1

9. Naming ions • Done systematically • Cation – if the charge is always the same, just write the name of the metal. • Transition metals can have more than one type of charge so we indicate the charge with roman numerals in parenthesis

10. Name these • Na +1 • Ca +2 • Al +3 • Fe +3 • Fe +2 • Pb +2 • Li +1

11. Write Formulas for These • Potassium ion • Magnesium ion • Copper (II) ion • Chromium (VI) ion • Barium ion • Mercury (II) ion

12. Naming Anions • When naming anions, always change the ending to - ide • Example – • F-1 Fluorine changes to Fluoride

13. Name these • Cl -1 • N -3 • Br -1 • O -2

14. Write these • Sulfide ion • Iodide ion • Phosphide ion

15. Ions in Ionic Compounds

16. Naming Binary Ionic Compounds • Binary compounds contain 2 elements • Ionic – contains a cation and an anion • To write the names just name the two ions

17. The compound must be neutral (have the same number of + and negative charges) • Examples: • NaCl = sodium chloride • MgBr2 = magnesium bromide

18. Write the names of the following: • KCl • Na3N

19. Writing Formulas • The charges have to add up to zero

20. Write the formula for Calcium Chloride • Calcium is Ca+2 • Chloride is Cl-1 • Ca+2Cl-1 would have a +1 charge • Need another Cl-1 • CaCl2

21. Write the formulas for these: • Lithium sulfide • Magnesium fluoride • Sodium chloride

22. Molecular Compounds Writing names and formulas

23. Molecular Compounds • Made of just nonmetals • Smallest piece is a molecule • Since there are no opposite charges, you can’t use charges to figure out how many of each atom

24. Easier • With ionic compounds you have to use the charges to figure out how many of each element. • With molecular compounds, the name tells you the number of atoms by using prefixes

25. Prefixes • 1 = mono- • 2 = di- • 3 = tri- • 4 = tetra- • 5 = penta- • 6 = hexa-

26. 7 = hepta- • 8 = octa- • 9 = nona- • 10 = deca-

27. To write the name, write two words • Prefix, name, prefix, name, -ide • One exception is we don’t write mono- if there is only one of the first element

28. Another rule: • There are no double vowels when writing names (oa oo)

29. Name these: • N2O • NO2 • Cl2O7 • CBr7 • CO2 • BaCl2

30. Write formulas for these • diphosphorus pentoxide • tetraiodide nonoxide • sulfur hexafluoride • nitrogen trioxide • carbon tetrahydride • phosphorus trifluoride