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S2 Chemistry

S2 Chemistry. Formula. Valency. The valency of an atom is the number of links which it can form. Valency. Atoms usually have a valency of 1, 2, 3 or 4 Magnesium has a valency of 2 and can be drawn as -. Mg. Valency. Valency. Valency. Valency. Draw the valency pictures for –

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S2 Chemistry

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  1. S2 Chemistry Formula

  2. Valency • The valency of an atom is the number of links which it can form.

  3. Valency • Atoms usually have a valency of 1, 2, 3 or 4 • Magnesium has a valency of 2 and can be drawn as - Mg

  4. Valency

  5. Valency

  6. Valency

  7. Valency • Draw the valency pictures for – hydrogen silicon aluminium nitrogen oxygen carbon argon sulphur

  8. Valency • The formula of a compound can be obtained by using the valency pictures

  9. Valency • The formula of a compound can be obtained by using the valency pictures • Eg hydrogen oxide

  10. Valency • The formula of a compound can be obtained by using the valency pictures • Eg hydrogen oxide First draw the valency pictures for hydrogen and oxygen.

  11. Valency H hydrogen O oxygen

  12. Valency H hydrogen O oxygen

  13. Valency H hydrogen O H oxygen

  14. Valency H hydrogen O H2O H oxygen

  15. Valency H hydrogen O H2O H oxygen All the links must be used.

  16. Valency Eg magnesium oxide Mg O

  17. Valency Eg magnesium oxide Mg O MgO

  18. Relative Atomic Mass • Atoms of different elements are different in size and are different in mass.

  19. Naming Compounds • The first part of the name comes from the element that is furthest to the left of the periodic table

  20. Naming Compounds • The first part of the name comes from the element that is furthest to the left of the periodic table • If the compound contains only 2 elements, the second part of the name changes to end in -ide

  21. Relative Atomic Mass • Atoms of different elements are different in size and are different in mass. • The mass is too small to be measured in grams so it is given a relative value

  22. Relative Atomic Mass

  23. Relative Atomic Mass

  24. Relative Formula Mass • Compounds can be given a formula mass by adding up all the individual elements.

  25. Relative Formula Mass • Compounds can be given a formula mass by adding up all the individual elements. H2O 2 hydrogens = 2 x 1 = 2 1 oxygen = 1 x 16 = 16

  26. Relative Formula Mass • Compounds can be given a formula mass by adding up all the individual elements. H2O 2 hydrogens = 2 x 1 = 2 1 oxygen = 1 x 16 = 16 18

  27. The Mole • A mole of any element is the relative atomic mass in grams. • Eg a mole of carbon has a mass of 12g

  28. The Mole • A mole of any compound is the relative formula mass in grams. • Eg a mole of water has a mass of 18g

  29. The Mole • A mole of a substance is known as the gram formula mass (gfm)

  30. The Mole • The following triangle can be used for mole calculations Mass of substance mass Number of moles n gfm Mass of 1 mole

  31. The Mole - example • Calculate the mass of 3 moles of water

  32. The Mole • Calculate the mass of 3 moles of water • From the triangle mass = n x gfm

  33. The Mole H2O 2 hydrogens = 2 x 1 = 2 1 oxygen = 1 x 16 = 16 18

  34. The Mole • Calculate the mass of 3 moles of water • From the triangle mass = n x gfm mass = 3 x 18g

  35. The Mole • Calculate the mass of 3 moles of water • From the triangle mass = n x gfm mass = 3 x 18g mass = 54g

  36. The Mole • How many moles are present in 9g of water.

  37. The Mole • How many moles are present in 9g of water. • From the triangle n = mass/gfm

  38. The Mole • How many moles are present in 9g of water. • From the triangle n = mass/gfm n = 9/18

  39. The Mole • How many moles are present in 9g of water. • From the triangle n = mass/gfm n = 9/18 n = 0.5 moles

  40. Word Equations Learning Intention We are learning to write word equations

  41. Word Equations All chemical reactions can be described using a word equation eg reactants products (what you start with) (what you end up with)

  42. Word Equations eghydrogen + oxygen hydrogen oxide

  43. Word Equations • Write a word equation for the following reaction

  44. Word Equations • Write a word equation for the following reaction • Carbon dioxide is formed when carbon burns in oxygen.

  45. Word Equations • Write a word equation for the following reaction • Carbon dioxide is formed when carbon burns in oxygen. carbon + oxygen carbon dioxide

  46. Formula Equations • Instead of using words, the formula for the reactants and products can be used instead. This is called a formula equation. • carbon + oxygen carbon dioxide

  47. Formula Equations • Instead of using words, the formula for the reactants and products can be used instead. This is called a formula equation. • carbon + oxygen carbon dioxide C + O2 CO2

  48. Formula Equations • Eg hydrogen + oxygen hydrogen oxide

  49. Formula Equations • Eg hydrogen + oxygen hydrogen oxide H2 + O2 H2O

  50. Diatomic Elements • Certain elements always go around in pairs. These are the diatomic elements.

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