Answer: (3) silicon
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Silicon (Si)
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: ethane
, propanone
and water 
2Al + 3CuCl2 ➡ 2AlCl3 + 3Cu.
Moles of Al = 1.2/27 = 0.045 moles
2 moles of Al reacts with 3 moles of CuCl2.
Therefore, 1 mole of CuCl2 reacts with =2/3 x moles of Al
= 2/3 x 0.045
= 0.03 moles.
The correct answer is A. All electrons become free and separate from the nuclei. In metallic bonds, the electrons of the metal atoms are delocalized. The electron in the electron sea can freely roam around or are free to flow.