Chemistry Ib Hl (Owned by Alexandra Juniper) Essay

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Approach your exams the IB way Chemistry HL IPBEPARED R Alexandra Juniper Jason Murgatroyd i 8. Bonding 8. Bonding Ionic bonding You should know: • ionic bonds form by electron transfer between elements of differing electronegativity, so between metals and non-metals • ionic bonding is due to the electrostatic attraction of oppositely charged ions • ionic bonding leads to the formation of a regular framework of alternating positive and negative ions described as a lattice. You should be able to: • deduce the formula of ionic compounds by knowing the details in the table Group number Electrons lost Charge on ion Group number Electrons gained Charge on ion 1 2 3 1 2 3 1+ 2+ 3+ 5 6 7 3 2 1 3– 2– 1– Be prepared • You should know and be able to use the formulas for carbonate (CO322), nitrate (NO32), sulfate (SO422), hydroxide (OH2), phosphate (PO432), hydrogencarbonate (HCO32) and ammonium (NH4+). Example What is the formula for the compound formed by calcium and nitrogen? A. CaN B. Ca2N C. Ca2N3 D. Ca3N2 Correct answer is D. Since calcium is in group 2 it is 2+, and nitrogen is in group 5 so it is 3–. You then need to “swap and drop” to balance the charges, so the correct answer is D. 51 8. Bonding Covalent bonding You should know: • covalent bonds form when electrons are shared between nuclei • dative covalent (coordinate) bonds form when both the electrons being shared have come from the same atom • single bonds are longer and weaker than double bonds, and triple bonds are shorter and stronger than double bonds, so CBC is more easily broken than CDC, which is more easily broken than CTC Diamond (C ) Structure giant: all C atoms bonded to 4 others Graphite (C ) giant: all C atoms bonded to 3 others in a layer covalent carbons in trigonal planar arrangement, bond angle 120°

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