1. Section 2.3—Chemical Formulas
We need to be able to read the formulas for chemicals in the antacids!

2. Reminders from Section 2.2
Your Chemistry Chart has lists of:
Common polyatomic ions
Multivalent metals
Covalent prefixes
Use your periodic table to determine the charges of common elements when they form ions

3. Binary Ionic compounds

4. Definitions Ionic bond- bond formed by attraction between + and - ions
Binary Ionic Compound- compound containing two elements—one metal and one non-metal +
Cation -
Anion
Ionic Compound

5. Metals & Non-Metals Ionic Bonds are between metals & non-metals H HeLi Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Lr Rf Db Sg Bh Hs Mt
Uun
Uuu
Uub
Uut
Metals
Metalloids
Non-metals

6. Identifying & Naming Binary Ionic
These compounds:
End in “-ide” (except “hydroxide and cyanide”)
Do NOT contain covalent prefixes
To write these formulas:
Write the symbol & charge of the first element (the metal, cation)
Write the symbol & charge of the second element (the non-metal, anion)
Add more of the cations and/or anions to have a neutral compound
Use subscripts to show how many of each type of ion is there.

7. Example #1
Sodium chloride

8. Example #1
Na+1
Cation
Sodium chloride
Anion
Cl-1
NaCl

9. NaCl Example #1 Sodium chloride Cation Anion Na+1 Na+1Cl-1 +1 + -1 = 0
The compound is neutral…no subscripts are needed.
Cl-1
NaCl

10. Example #2
Calcium bromide

11. Example #2
Ca+2
Cation
Calcium bromide
Anion
Br-1

12. CaBr2 Example #2 Calcium bromide Cation Anion Ca+2 Ca+2Br-1
= +1
Anion
Ca+2Br-1Br-1
Br-1
= 0
CaBr2
The subscript “2” is used to show that 2 anions are needed.

13. Write the following chemical formulas
Let’s Practice
Cesium chloride
Potassium oxide
Calcium sulfide
Lithium nitride
Example:
Write the following chemical formulas

14. Write the following chemical formulas
Let’s Practice
Cesium chloride
Potassium oxide
Calcium sulfide
Lithium nitride
CsCl
K2O
CaS
Li3N
Example:
Write the following chemical formulas

15. Polyatomic Ionic Compounds

16. Definition
Polyatomic Ion- more than one atom that together have a charge
Polyatomic Ionic Compound- compound containing at least one polyatomic ion +
Cation -
Polyatomic
Anion
Polyatomic Ionic
Compound

17. Identifying & Naming Polyatomic Ionic
These compounds:
Do not end with “-ide” (except hydroxide & cyanide)
Do not use covalent prefixes
To write these formulas:
Write the symbol & charge of the cation & anion
Add additional cations or anions to have a neutral compound
Use subscripts to show the number of ions
When using subscripts with a polyatomic ion, you must put the polyatomic ion in parenthesis.

18. Example #3
Sodium carbonate

19. Example #3
Na+1
Cation
Sodium carbonate
Polyatomic
Anion
CO3-2

20. Na2CO3 Example #3 Sodium carbonate Cation Polyatomic Anion Na+1
= -1
Polyatomic
Anion
Na+Na+CO32-
= 0
CO3-2
Na2CO3
The subscript “2” is used to show that 2 cations are needed.

21. Example #4
Magnesium nitrate

22. Example #4
Mg+2
Cation
Magnesium nitrate
Polyatomic
Anion
NO3-1

23. Mg(NO3)2 Example #4 Magnesium nitrate Cation Polyatomic Anion Mg+2
= 1
Magnesium nitrate
Mg+2NO3- NO3-
Polyatomic
Anion
= 0
NO3-1
The subscript “2” is used to show that 2 anions are needed.
Mg(NO3)2
Use parenthesis when adding subscripts to polyatomic ions

24. Write the following chemical formulas
Let’s Practice
Sodium nitrate
Calcium chlorate
Potassium sulfite
Calcium hydroxide
Example:
Write the following chemical formulas

25. Write the following chemical formulas
Let’s Practice
Sodium nitrate
Calcium chlorate
Potassium sulfite
Calcium hydroxide
NaNO3
Ca(ClO3)2
K2SO3
Ca(OH)2
Example:
Write the following chemical formulas

26. Multivalent Metals

27. Definition
Multivalent Metal- metal that has more than one possibility for cationic charge

28. Identifying & Naming Multivalent Metals
These compounds:
Will have roman numerals
To write these formulas:
Same as binary ionic or polyatomic ionic.
The roman numerals tell the charge of the metal (cation)

29. Example #5
Iron (III) oxide

30. Example #5
Fe+3
Cation
Iron (III) oxide
Anion
O-2

31. Fe2O3 Example #5 Iron (III) oxide Cation Anion Fe+3 Fe+3O2-
= -1
Iron (III) oxide
Fe+3Fe+3O2-O2-
Anion
= 0
O-2
The subscript “2” and “3” are used to show the numbers of atoms needed.
Fe2O3

32. Example #6
Copper (II) nitrate

33. Example #6
Cu+2
Cation
Copper (II) nitrate
Polyatomic
Anion
NO3-1

34. Cu(NO3)2 Example #6 Copper (II) nitrate Cation Polyatomic Anion Cu+2
= 1
Copper (II) nitrate
Cu+2NO3-NO3-
Polyatomic
Anion
= 0
NO3-1
Use parenthesis when adding subscripts to a polyatomic ion
Cu(NO3)2

35. Write the following chemical formulas
Let’s Practice
Iron (II) nitrate
Copper (I) chloride
Lead (IV) hydroxide
Tin (II) oxide
Example:
Write the following chemical formulas

36. Write the following chemical formulas
Let’s Practice
Iron (II) nitrate
Copper (I) chloride
Lead (IV) hydroxide
Tin (II) oxide
Fe(NO3)2
CuCl
Pb(OH)4
SnO
Example:
Write the following chemical formulas

37. Binary Covalent Compounds

38. Definition Covalent bond atoms share electrons
Binary Covalent Compound compound made from two non-metals that share electrons
Non
metal
Non
metal
Covalent compound

39. Identifying & Naming Binary Covalent
These compounds:
Use covalent prefixes
To write these formulas:
Write the symbols of the first and second element
Use the covalent prefixes (assume the first element is “1” if there’s no prefix) as the subscripts to show number of atoms.
Atoms do not form charges when bonding covalently…you DO NOT need to worry about charges with this type!

40. Dinitrogen Tetraoxide
Example #7
Dinitrogen Tetraoxide

41. Dinitrogen Tetraoxide
Example #7
“Di-” = 2 N
Dinitrogen Tetraoxide O
“Tetra-” = 4
N2O4

42. Example #8
Silicon dioxide

43. Silicon dioxide SiO2 Example #8 Si O
“Mono-” is not written for the first element Si
Silicon dioxide O
“Di-” = 2
SiO2

44. CAUTION!!! “di” and “bi” do not mean the same thing! di- bi-
Stands for “2” in covalent compounds
Means there’s a hydrogen in the polyatomic anion
Carbon dioxide = CO2
Sodium biphosphate = Na2HPO4

45. Write the following chemical formulas
Let’s Practice
Carbon monoxide
Nitrogen dioxide
Diphosphorus pentaoxide
Example:
Write the following chemical formulas

46. Write the following chemical formulas
Let’s Practice
Carbon monoxide
Nitrogen dioxide
Diphosphorus pentaoxide CO
NO2
P2O5
Example:
Write the following chemical formulas

47. Nomenclature Summary Writing Chemical Formulas
Does not contain covalent prefixes
Does contain covalent prefixes = Binary Covalent compound
Ends with “-ide” (except hydroxide & cyanide) = Binary Ionic
All others = Polyatomic Ionic

48. Write the following chemical formulas
Mixed Practice
Magnesium hydroxide
Copper (II) nitrate
Iron (III) oxide
Nitrogen dioxide
Sodium bicarbonate
Example:
Write the following chemical formulas

49. Write the following chemical formulas
Mixed Practice
Magnesium hydroxide
Copper (II) nitrate
Iron (III) oxide
Nitrogen dioxide
Sodium bicarbonate
Mg(OH)2
Cu(NO3)2
Fe2O3
NO2
NaHCO3
Example:
Write the following chemical formulas