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week 1, term 3

posted 19 Jul 2014, 20:54 by Maree Pullar   [ updated 19 Jul 2014, 20:55 ]

This week you will be learning about:

·         Covalent bonding

·         Lewis diagrams

·         Polar and non-polar bonds

·         Shapes of molecules (will be discussing this at Friday’s VC)

Covalent bonding-

·         Valence electrons are shared

·         Form between atoms of the non-metals

Electronegativity-

·         Is the measure of how strongly bonding electrons are attracted to the nucleus of an atom in a bond.

·         Electronegativities increase across a period

·         Electronegativities decrease down a group

Lewis structures-

·         Only use the valence electrons of the atoms

·         A pair of electrons can be shown  as 2 dots or a single line

·         All atoms try to get an octet ( 8 electrons in their outer shell). The exception is hydrogen which must get 2 electrons in its outer shell.

·         Watch this video clip: https://www.youtube.com/watch?v=1ZlnzyHahvo

The 5 rules for drawing Lewis structures are:

1.       Find the total number of valence electrons

2.       Put the least electronegative atom at the centre of the molecule

3.       Put 2 electrons between the atoms to form a chemical bond

4.       Complete octets on the outside atoms

5.       If the central atom doesn’t have an octet, move electrons from outer atoms to form double or triple bonds.

Things to do:

·         Read p99-102 in the study guide

·         Do Act 9A in study guide

·         Do Act 4B in the learning workbook

·         Do p44/45 in the attachments (there will be an overlap of some of the molecules but lots of practise will make you an expert at drawing Lewis structures).

·         Read p103-105 in the study guide

·         Make notes on:

1.       Definition of electronegativity

2.       If 2 atoms have the same electronegativity, the bond is non-polar.

3.       If the electronegativity difference is between 0.4 and 1.6, the bond is polar covalent

4.       If the electronegativity difference is greater than 1.6, ionic bonding occurs. (see the table at the bottom of p105.

·         Do Act 9B in study guide

·         Do Act 4C in the learning workbook

·         Do p46/47 in the attachments

·         Read about shapes of molecules p106-110 before the VC and watch the video clips below.

·         https://www.youtube.com/watch?v=-pq2wum1uDc

·         https://www.youtube.com/watch?v=nxebQZUVvTg

 

 

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Maree Pullar,
19 Jul 2014, 20:54
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