how to draw lewis structure for the following molecules,perdict their shape& lablel as polar or non-polar?

Question

C2H2,CBr4,

Answer 1

For lewis dot structure, first you need to figure out which is the central atom. C is for both (H always goes on the outside, and there are 4 Br, 1 C therefore C is the central atom). Then you need to know how many valence elctrons; for this you use your periodic table (look at which # column the element is in: H has 1 valence e-, C 4, can you figure out Br?). Then you connect the elements with a line (=2 electrons) then you start adding dots to complete the octet. If you run out of electrons before completing the octet then you need to have double bonds somewhere, and if you have too many electrons then you just add a lone pair to the central atom.

To predict shapes, you need to know how to do VSPER models. After you've drawn the shape, look to see how many total pairs, how many bonds, and how many lone pairs then you find the shape based on the VSEPR model chart. (CBr4 is 4 total bonds, 4 pairs, 0 lone pairs, can you tell me the shape?)

To figure out polar or non polar, you need to look at the shape; polar ones have the pairs on one end or nonsemetrical; nonpolar are semetrical.

If you can't figure the answers out with help, email me and I'll try and help you some more.