1. Elements and Compounds

2. Matter Any thing with mass and volume

3. Matter can be classified based on what it is made of and how it behaves

4. Element A substance that cannot be broken down into simpler substances It contains only one kind of atom

5. There are about 118 known elements, but there are many millions of chemical compounds.

6. Each element is represented by a Symbol The first letter is capitalized The second letter (if present) is lower case C- carbon O- oxygen Co- cobalt

7. Each element has unique characteristics

8. But when elements combine, they lose their unique characteristics and form a new substance with different characteristics = ?

9. Hydrogen + Oxygen = Water

10. We call this new substance a compound Compound- – a type of substance made of atoms of two or more elements joined by chemical bonds

11. Compounds are represented by chemical formulas It will tell you: A. the elements in that compound B. the number of atoms of that element

12. Writing a chemical formula for a compound 1. Write the symbol of the elements in that compound (H and O) 2. Use a subscript to identify how many atoms of each element are in the compound. (no subscript for a single atom)

13. Common Compound Formulas Carbon Dioxide – CO 2 Carbon monoxide -CO - (no subscripts since only one atom is present) Hydrogen peroxide –H2O2–H2O2 Methane – CH 4

14. Compounds can only be changed back into individual elements through a chemical reaction

15. Compounds usually form when a metal (green)and a non-metal (yellow) combine

16. Unit 7, 16 Molecules A molecule is a group of atoms joined together. It is the smallest part of an element or compound that can exist independently.

17. There are two types of molecules: – Molecules of elements: (All the same atoms in the molecule) e.g. Cl 2, C 3. – Molecules of compounds: (Different atoms in the molecule) e.g. H 2 O, HCl, H 2 SO 4.

18. Molecule examples Molecules of elements (top row) Molecules of compounds (bottom row)

19. Unit 7, 19 Elements which form molecules Elements that end in –ine and –gen exist as diatomic (2 atom) molecules in their natural form.

21. Counting atoms in compounds NaCl First identify which how many different elements are in the compound (2) Name those elements (Na- sodium, Cl- Chlorine) Count how many atoms of each element are present by looking at the subscript (1 of each) Add up the atoms to determine the total number of atoms in that molecule (2)

23. Formula# of elements Name of elements # of atoms of each element Total # of atoms NaCl 2 Sodium Chlorine 1111 2 H 2 SO 4 3 Hydrogen Sulfur Oxygen 2 1 4 2+1+4 = 7 NaOH CHCl 3 CaCO 3

24. Element or Compound? Copper

25. Element or Compound? Copper

26. Element or Compound? Table Sugar

27. Element or Compound? Table Sugar

28. Element or Compound? Diamond

29. Element or Compound? Diamond

30. Element or Compound? Salt

31. Element or Compound? Salt

32. Element or Compound? Neon Gas

33. Element or Compound? Neon Gas

34. Element or Compound? Pure Water

35. Element or Compound? Pure Water

36. Element or Compound? Aluminum

37. Element or Compound? Aluminum

38. Element or Compound? Silver

39. Element or Compound? Silver

40. Element or Compound? Oxygen

41. Element or Compound? Even Ozone (O 3 ) is an element, it only has one type of atom (O)!

42. Element or Compound? Chocolate

43. Element or Compound? Chocolate