Many thanks for that introduction to Taj’s question. the images for the three metals show the electrons in ‘shells’ around the core metal atom. Taj, you may be interested to know that the electron was discovered in 1897 by Thomson and the arrangement of electrons in shells around the nucleus by Neils Bohr in the 1920’s ….only 100 years ago.
Look at the ‘shells’ …the first one near the nucleus of all the metal atoms contains 2 electrons, the second shell contains 8 electrons, the third shell contains 18 electrons , the fourth shell contains 32 electrons (which are subdivided into three levels).
It is the outermost shell that is the important one when it comes to chemical activity. If the shell is full (has its load of electrons) the atom is unreactive (noble gases). If the shell is not full …the atom is reactive and the reactivity seems to be linked to how empty the outermost shell is and how close the shell is to the atomic nucleus.
Think about these rules when you look again at the sodium, copper and gold atoms.
Thanks for the question.