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 
wrong. If its for the study island its potential energy only.
Answer:
trigonal planar
Explanation:
Tri=three, three-dimensional arrangement of the atoms that constitute a molecule.
Hope this helps!! Please mark brainliest