This document provides instructions on writing chemical formulas. It explains that chemical symbols represent elements and come from element names. Subscript numbers indicate the number of atoms in a compound. Ionic formulas are written with the metal first followed by the nonmetal and hyphenated name. Covalent prefixes like mono, di and tri are used to denote the number of non-metal atoms bonded to the central atom. Roman numerals specify the metal's oxidation state in some compounds. The document uses examples to demonstrate how to apply these rules to write formulas for ionic and covalent compounds.

1. Unit 12: Writing and Naming Chemical Formulas Physical Science

2. Chemical Symbols

3. How to writing chemical formulas Use the chemical symbol for each element Usually, the element abbreviations come from the word (He for Helium or Ti for Titanium) Some elements have just one letter, such as H for Hydrogen or N for Nitrogen

4. How to writing chemical formulas Sometimes the abbreviation does not look like the element such as: K for Potassium Na for Sodium Pbfor Lead Cu for Copper Ag for Silver Au for Gold

5. How to writing chemical formulas That is because their name came from Latin or other languages K for Potassium (Kalium) Na for Sodium (Natrium) Pb for Lead (Plumbum) Cu for Copper (Cuprum) Ag for Silver (Argentum) Au for Gold (Aurum)

6. The 11 Odd Elements to Memorize

7. How to writing chemical formulas Most elements have two letters Always capitalize the first letter and use lower case on the second one. Example: Cobalt is Co If you used two capitals (CO), it would be mistaken for Carbon Monoxide which has one Carbon (C) and one Oxygen (O)

8. Subscript Numbers The subscript number specifies how many atoms of that element you have N2 is a nitrogen molecule with two atoms C2H4 has two carbons and four hydrogens. CO2 is carbon dioxide and contains one carbon and two oxygens If no number is listed, it means there is only one

9. More Examples C2H3Cl what elements and how many of each?

10. More Examples C2H3Cl what elements and how many of each?

11. More Examples H2SiCl2 what elements and how many of each?

12. More Examples H2SiCl2 what elements and how many of each?

13. Numbers in Front Versus Behind What should this molecule look like? For example CH4=

14. Numbers in Front Versus Behind What should this molecule look like? It is called Methane For example CH4=

15. Numbers in Front When there are large numbers in front, that tells you how many molecules there are. For example 3CH4 =

16. Numbers in Front When there are large numbers in front, that tells you how many molecules there are. For example 3CH4 = 3 methane molecules 12NaOH = ?

17. Numbers in Front When there are large numbers in front, that tells you how many molecules there are. For example 3CH4 = 3 methane molecules 12NaOH = 12 different Sodium Hydroxide molecules.

18. Part One: Ionic Formulas Part One: Writing Ionic Formulas Always say the metal name first and then the non-metal with an -ide

19. Part One: Ionic Formulas Part One: Writing Ionic Formulas Example: CaCl2 would be called calcium chloride

20. Part One: Ionic Formulas Part One: Writing Ionic Formulas Example: What if you saw the name Magnesium chloride …What is the formula?

21. Part One: Ionic Formulas Magnesium Chloride = Mg+2 Cl-1

22. Part One: Ionic Formulas Magnesium Chloride = MgCl2 Mg+2 Cl-1

23. Part One: Ionic Formulas OK, here is one for you Magnesium Phosphate Magnesium= Mg2+ Phosphate = PO43- Remember, the charges have to balance

24. Part One: Ionic Formulas OK, here is one for you Magnesium Phosphate Magnesium= Mg2+ Phosphate = PO43- Remember, the charges have to balance 2 X 3 = 6

25. Part One: Ionic Formulas OK, here is one for you Magnesium Phosphate Magnesium= Mg2+ Phosphate = PO43- Remember, the charges have to balance Mgx(PO4)y 2 X 3 = 6 +6 -6

26. Part One: Ionic Formulas OK, here is one for you Magnesium Phosphate Magnesium= Mg2+ Phosphate = PO43- Remember, the charges have to balance Mg3(PO4)2

27. Examples of naming for metals with multiple charges

28. Examples of naming for metals with multiple charges

29. Part One: Ionic Formulas What about Iron (II) Oxide Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2-

30. Part One: Ionic Formulas What about Iron (II) Oxide Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2- Step Two: See how to balance the charges Step Three: Find the combination that balances

31. Part One: Ionic Formulas What about Iron (II) Oxide Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2- Step Two: See how to balance the charges Step Three: Find the combination that balances Iron (II) Oxide = FeO

32. How do you know if you use Roman numerals? Do not use Roman Numerals for groups 1 or 2 as they are always (+1) and (+2) accordingly. K = +1 and Ca = +2 +1 +2

33. How do you know if you use Roman numerals? Do not use Roman numerals for anything in the P-block since they tend to form covalent bonds. The exceptions are Tin (Sb) and Lead (Pb)

34. How do you know if you use Roman numerals? Do not use Roman numerals for Zn or Ag because they have dominant oxidation states that rarely change: Ag = +1 and Zn = +2.

35. Prefixes for Covalent Bonds Example 1 = Mono Carbon Monoxide (CO)

36. Prefixes for Covalent Bonds Example 1 = Mono Carbon Monoxide (CO) 2 = Di Carbon Dioxide (CO2)

37. Prefixes for Covalent Bonds Example 1 = Mono Carbon Monoxide (CO) 2 = Di Carbon Dioxide (CO2) 3 = Tri Nitrogen Triiodide (NI3) As you can see, you don’t label the first with a prefix unless it is more than one

38. Prefixes for Covalent Bonds Example 1 = Mono Carbon Monoxide (CO) 2 = Di Carbon Dioxide (CO2) 3 = Tri Nitrogen Triiodide (NI3) 4 =Tetra DinitrogenTetroxide (N2O4) As you can see, you don’t label the first with a prefix unless it is more than one

39. Prefixes for Covalent Bonds Example 1 = Mono Carbon Monoxide (CO) 2 = Di Carbon Dioxide (CO2) 3 = Tri Nitrogen Triiodide (NI3) 4 =Tetra DinitrogenTetroxide (N2O4) 5 = Penta Phosphorus Pentachloride (PCl5) As you can see, you don’t label the first with a prefix unless it is more than one

40. Prefixes for Covalent Bonds Example 1 = Mono Carbon Monoxide (CO) 2 = Di Carbon Dioxide (CO2) 3 = Tri Nitrogen Triiodide (NI3) 4 =Tetra DinitrogenTetroxide (N2O4) 5 = Penta Phosphorus Pentachloride (PCl5) 6 = Hexa Sulfur Hexaflouride (SF6) As you can see, you don’t label the first with a prefix unless it is more than one

41. Drawing Covalent Compounds In general, the first named compound is the central compound. Sulfur dioxide Nitrogen Triiodide Carbon Tetrachloride