5. In a sample of pure copper, all atoms have atomic numbers which are
(1) the same and the atoms have the same number of electrons
(2) the same but the atoms have a different number of electrons
(3) different but the atoms have the same number of electrons
(4) different and the atoms have a different number of electrons

(1) the same and the atoms have the same number of electrons

Explanation:

In a pure sample of copper, all the atoms have atomic numbers which are the same and the atoms have the same number of electrons.

Pure samples of a substance have a definite composition and are homogeneous all through.

To show this all the atoms that makes up the substance have the same number of electrons because they are of the same atom.

these nuts