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 
Answer:
the first thing you do is do your experiment then title it. then state the purpose of the experiment. included a summary of the experiment. make a list of the materials you used. present all the steps in order to make the experiment possible. note any changes to the original procedure. this is basically the steps you have to do in order to make your scientific experiment.
Answer:
Iodine
Explanation:
It's in the same group as chlorine.
<span>There is a direct correlation between the period number and the energy level for valence electrons. For example, the H and He elements, in period 1, have their outer electrons in the energy level "1". This continues down the rows: all the elements in period 2 have their principal energy level as n = 2, period 3 has n = 3, and so on.</span>
