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Published byStephen Robbins Modified over 9 years ago
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Bonding Why do atoms bond? The octet rule – all atoms bond so they have 8 electrons in their outer shell, so that it is FULL.
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Exceptions to this are: The Noble gases (group 8) Hydrogen Already have full outer shells The first shell can only fit two electrons in it
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Types of bonding 1.Ionic 2.Covalent
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1 Ionic Metals and non- metals combine to make compounds How do they do this? They form ions
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The metal loses electrons from its outer shell to form a positive ion Na Sodium atom (Na) Sodium ion (Na + )
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How many electrons do atoms lose or gain? Metals Group 1 elements lose one electron to obtain a full octet e.g. Na [2,8,1] → Na + [2,8] Group 2 elements lose two electrons to obtain a full octet e.g. Mg [2,8,2] → Mg 2+ [2,8]
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Non-metals Group 7 elements gain one electron to obtain a full octet e.g. Cl [2,8,7] → Cl - [2,8,8] Group 6 elements gain two electrons to obtain a full octet e.g. O [2,6] → O 2- [2,8] How many electrons do atoms lose or gain?
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Properties of ionic compounds Very high melting and boiling points Brittle Conduct electricity when molten and in solution
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Li Na K
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Size
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Li Na K Size Outer electron held more loosely
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Li Na K Size Outer electron held more loosely Explains increasing reactivity
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Ionic Bonding Ionic bonds form between metals and non- metals Metal atoms lose electrons to form positive ions Non-metal atoms gain electrons to form negative ions The oppositely charged ions attract one another
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Sodium and Chlorine 11+ 17+ 11+ and 10- = 1+ Na + 17+ and 18- = 1- Cl - + -
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Magnesium and Oxygen 12+8+ 12+ and 10- = 2+ Mg 2+ 8+ and 10- = 2- O 2- 2+ 2-
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Magnesium and Chlorine 17+ and 18- = 1- Cl - 17+ and 18- = 1- Cl - 12+ and 10- = 2+ Mg 2+ 17+12+17+ - - 2+
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Covalent Bonding Covalent bonds form between non-metal atoms Covalent bonds involve sharing a pair of electrons
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Hydrogen and Hydrogen H H2H2 H
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Nitrogen and Hydrogen (Ammonia) H H H N NH 3
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Hydrogen and Oxygen H2OH2O H H O
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