Question

why does iron appear different from copper and aluminium​

Answer 1

It has to do with the different physical properties of these elements, which ultimately depend on their electrons, protons and neutrons.

Answer 2

Answer:

Iron is darker than aluminium, the two being light gray and white-ish, respectively. Iron typically undergoes fairly slow oxidisation, forming a flaky red rust. Aluminium simply gets dull, retaining its white colour. Copper has a characteristic brown-red colour that's aptly described as “copper”.