An introduction and review of concepts required for success in year 12 biology (BIO4U).

5. 1.1 Atoms and Bonding

7. Atoms and Elements

13. Ionic Bonding sodium atom (Na) sodium ion (Na + ) 11 protons (+) 10 electrons (-) one (+) charge 11p 12n 11p 12n + electron given up

14. Ionic Bonding 17p 18n 17p 18n electron accepted 17 protons (+) 18 electrons (-) one (-) charge chlorine atom (Cl) chlorine ion (Cl - ) -

15. Ionic Bonding 11p 12n 17p 18n Na Cl +

16. Ionic Bonding sodium chloride (NaCl) 11p 12n + 17p 18n -

18. Covalent Bonding Cl + Cl 17p 18n 17p 18n

19. Covalent Bonding Cl-Cl chlorine gas (Cl 2 ) 17p 18n 17p 18n

23. Electronegativity larger eletronegativity - smaller electronegativity = difference in electronegativity

24. Electronegativity Examples: O 2 -> oxygen has an EN of 3.44 3.44 - 3.44 = 0 ∆ EN = 0, therefore each atom in an oxygen molecule has an equal attraction for the bonding pair of electrons. This is a covalent bond.

25. Electronegativity Examples: HCl -> H has an EN of 2.20, Cl has an EN of 3.16 3.16 - 2.20 = 0.96 ∆ EN = 0.96, therefore chlorine has a slightly great pull on the bonding pair of electrons. This is a polar covalent bond.

26. Electronegativity Examples: NaCl -> Na has an EN of 0.93, Cl has an EN of 3.16 3.16 - 0.93 = 2.23 ∆ EN = 2.23, therefore chlorine has a substantially greater pull on the bonding pair of electrons. This is an ionic bond.

30. Hydrogen Bonding hydrogen bonding in water