|MadSci Network: Chemistry|
Thank you for this question. Metal atoms are generally much closer together than atoms of non-metals. We describe the structure of metals as “close-packed”. The atoms are held together by a “sea of electrons”, which keeps them very close, although it allows the rows of atoms to slide past each other (hence metals are malleable and ductile). Non-metals on the other hand are often made of small, separate molecules. The forces between the molecules in the solid are weak and therefore the distances between particles are greater. This makes non-metals less dense.
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