Chromium: Chromium is a Lustrous,brittle and hard metal.Its colour is silver gray and it can be highly polished.It does not tarnish in air.It is unstable in oxygen ,it immediately produces a thin oxide layer that is impermeable to oxygen and protects the metal below.
Copper: An important chemical property of copper is that the way it reacts with oxygen.It is a ductile metal with high thermal and electrical conductivity.Pure copper is soft and malleable.