16. Metals have a structure containing delocalised electrons, meaning they can conduct electricity as they allow movement of charged particles. 17. groups of elements (columns) react in the same way, but depending on whether they group tends to lose or gain electrons the reactivity can increase or decrease when going down the group (column) 18. O2 is non polar as there is no difference in electronegativity between two oxygen atoms (they are the same). CO2 is non polar, it has polar bonds (O is more electronegative than C) but as it is symmetrical there is no polarity in the molecule. 19. Water is polar as the lone pairs on the O repel the delta + H groups so that the HOH angle is around 109deg, so water molecules create polar interactions which each other. These polar interactions require energy to break, so water has a higher boiling point than other small molecules which don't have these interactions. 20. The metal used is tough, and the horseshoe is usually heated meaning the metal will act slightly more viscous (closer to liquid). This means it can be moulded better, and then when its cooled it will become stronger and more brittle. 21. Well N2 + H2 --> NH3, by the haber process, so nitrogen:hydrogen ratio is 1:3. But what they want you to say is that nitrogen has 5 electrons and hydrogen has 1 and you're aiming for eight so you need N (5) + 3 Hs (3*1=3) to make NH3 (8 electrons around N) 22. Na and H, as this reduces the valence shell number and therefore reduces the energy state of the atom 23. Ar, its very stable as its octet is filled, meaning to fill or empty its octet it would have to lose or gain 8 electrons which is extremely hard 24. Oxygen, as it would accept the electrons donated by the 2 Na atoms, and fill its octet while emptying both the Na's 25. N2 and O2 are both covalently bonded, Oxygen forms a double bond to itself like this O=O and nitrogen forms a triple bond to itself like this N<span>≡N </span><span>Hope that helps :) and make sure you learn this, it'll come back and bite you when you need it for a test</span>
