Isomers of dibromoethene molecule, c2h2br2. one of them has no net dipole moment, but the other two do. draw lewis structures for each of these isomers. include h atoms.

No net dipole moment: 1,2-dibromoethene (trans-isomer)

Net dipole moment: 1,2-dibromoethene (cis-isomer), 1,1-dibromoethene

Explanation:

A Lewis Structure is a simplified representation of the valence shell electrons in a molecule. It shows arrangement of the electrons around individual atoms in a molecule. Electrons are shown as "dots" or for bonding electrons as a line between the two atoms (double line for a double bond).

Isomers are compounds with the same chemical composition but different physical arrangement of atoms. Isomers can be split into two main types, structural isomers and stereo-isomers. Structural isomers can be split into chain (different arrangement of atoms/molecules), position (different position of functional group) and functional (different functional group) isomers. Stereo-isomers can be split into geometric (different atoms around a bond with limited rotation) and optical (non-super-imposable mirror images) isomers.

Dipole moments occur when there is a separation of charge. It can occur between two ions in an ionic bond or between atoms in a covalent bond due to a difference in electro-negativity. When one atom is more electro-negative than another, that atom pulls more tightly on the shared pair of electrons, or when one atom has a lone pair of electrons and the difference of electro-negativity vector points in the same way a net dipole moment occurs. One of the most common examples is the water molecule, which consists of one oxygen and two hydrogen atoms. The differences in electro-negativity and lone electrons gives oxygen a partial negative charge and each hydrogen a partial positive charge.

In the attached image, 3 isomers of dibromoethene can be seen. Isomer A and B are geometric stereo-isomers. Isomer C is a position structural isomer. All 3 isomers have polar C-Br bonds as bromine is more electro-negative than carbon. Isomer A has the bromine atoms pulling the electron cloud in opposite directions (180° to each other) thus there is no net dipole moment. Isomers B and C have the bromine atoms pulling electron cloud in a direction not 180° to each other so they do not cancel each other out resulting in a net dipole moment.

c, liquids evaporate, creating a gas