A Zwitter ion is

an ion with a positive charge and a negative charge at different points in it

The correct answer is option 3. an ion with a positive charge and a negative charge at different points in it.

A Zwitter ion is an ion with a positive charge and a negative charge at different points in it. A zwitterion is a neutral molecule with both positive and negative charges, but the overall charge of the molecule is zero. It typically occurs in amino acids and certain other molecules where there are both acidic and basic functional groups. In the case of amino acids, the amino group \((-NH_2)\) becomes positively charged by losing a hydrogen ion \((H^+)\) and the carboxyl group \((-COOH)\) becomes negatively charged by gaining a hydrogen ion \((H^+)\), resulting in a molecule with both positive and negative charges. This internal charge balancing results in a net neutral charge for the zwitterion.

Summary:

Zwitterion: A molecule with both positive and negative charges, but the overall charge is neutral.

Occurrence: Commonly found in amino acids and certain other molecules with both acidic and basic functional groups.

Charge Balancing: The positive and negative charges within the molecule balance each other out, resulting in a net neutral charge.

Significance: Zwitterions are important in biochemistry and play a crucial role in the structure and behavior of molecules such as amino acids in biological systems.

So, the correct definition is: an ion with a positive charge and a negative charge at different points in it.