Question

define element and Residue

Answer 1

A complete residue system is a set of integers containing one element from each class, so would be a completeresidue system for (mod 6).

Answer 2

An element is a substance whose atoms all have the same number of protons: another way of saying this is that all of a particular element's atoms have the same atomic number. Elements are chemically the simplest substances and hence cannot be broken down using chemical reactions.
something that remains after a part is removed, disposed of, or used; remainder; rest; remnant. Chemistry. residuum(def 2). an atom or group of atoms considered as a group or part of a molecule. that part remaining as a solid on a filter paper after a liquid passes through in the filtration procedure.