Hi..I have collected Lincoln one cent the year of 1982 D all these coins looking same no doubt but if we do weighing these aren't have same weight 6 nos of 3.10 gm and another one has 2.5 gm. I don't know how is it error?

What you are going to want to look for is the Large Date vs Small Date. If you go into Google and type in 1982 Large Date vs Small Date, then it will show you an image of what you should be looking for. However, 9,999 times out of 10,000, these won't be the rare variety.

Ever since they turned to replacing the copper with zinc and then layering some copper over the 1 cent coins, the weight has become an issue. What makes the "value" is a printing error such as mispelled or missing words or symbols or even double-punching a single coin. If not, only an immulately printed coin (one with super luster or rainbow shine which you can count all 6 steps to the lincoln memorial one the back) will be worth your time.