2. For each of the following say if it is ionic, covalent.

6.  Blue crystals  Will dissolve  Conducts electricity when molten

7.  Dangerous substance  Contains carbon  Made by incomplete combustion

8.  MgO

9.  diatomic green gas  Melting point -101 °C  Boiling point -34.6 °C

10.  Very hard  Tetrahedral structure  Boiling point 2230 °C  Used in desiccants

11.  Pungent smelling gas  Can be used in explosives

12. Potassium chloride

13. IONIC NaCl Copper Sulfate MgO Potassium chloride COVALENT Methane Oxygen Carbon Monoxide CL 2 Silicon Dioxide Metals bond to non metals to form ionic compounds. When non metals bond a covalent compound is formed

14. When non-metal atoms react together, they need to gain electrons to fill their outer shell and become stable. They can only do this if they share electrons with each other. The atoms share electrons so there is a strong force that joins the atoms together. This is called a covalent bond. H H incomplete outer shells H H both atoms have a full outer shell solid line HH – – HH

15. Which other elements form diatomic molecules?

16. HH Cl O O The covalent bonds between the atoms are strong which is why the atoms go around in pairs.

17. Remember more than one pair of electrons can be shared. Draw the molecules in both ways (only the outer shell)

18. Chlorine (2.8.7) needs 1 more electron to have a completely full outer shell. Cl Cl 2 or Cl–Cl To achieve this, it can share an electron with another chlorine atom. This creates a single bond. Cl

19. O Oxygen (2.8.6) needs 2 more electrons to have a completely full outer shell. O 2 or O=O To achieve this, it can share two electrons with another oxygen atom. This creates a double bond. O O O

20. Nitrogen (2.8.5) needs 3 more electrons to have a completely full outer shell. N 2 or N≡N It can share three electrons with another nitrogen atom to do this. This creates a triple bond. N N N N

21. Remember more than one pair of electrons can be shared. Draw the molecules in both ways (only the outer shell)

22. Covalent bonding can take place between atoms of different elements to create molecules of covalent compounds. These covalent bonds can be single, double or triple. Both hydrogen (1) and chlorine (2.8.7) need 1 more electron to fill their outer shell. By sharing one electron each, they can fill their outer shells and become stable. HCl or H Cl Cl H H 2 + Cl 2   2HCl

23. O Oxygen (2.6) needs 2 more electrons, but hydrogen (1) only needs 1 more. How can these two elements be covalently bonded? The oxygen atom shares 1 electron with 1 hydrogen atom, and a second electron with another hydrogen atom. H 2 O or H O H H H

24. N NH Electron configuration Electrons needed Ratio of atoms How are nitrogen and hydrogen bonded in ammonia? 2.51 3131 1313 H H NH 3 or H N H H H

25. CH Electron configuration Electrons needed Ratio of atoms How are carbon and hydrogen bonded in methane? 2.41 4141 1414 CH 4 or H C H H H C H H H H