
The 2 in front of
in
is <u>Coefficient.</u>
_____________________________
The
after
in the same equation is <u>sub </u><u>script</u><u>.</u>
_____________________________
There are two atoms of
in 
_____________________________

Hey there!
Volume in mL :
1.68 L * 1000 => 1680 mL
Density = 0.921 g/mL
Therefore:
Mass = density * Volume
Mass = 0.921 * 1680
Mass = 1547.28 g
The answer to your question is letter A! Hope that helps
The answer would be A) cells!!
The difference between short period and long period is based upon the number of elements in each period. Shortest period is the first period which contains elements, while the longest period is the 6th period which contains 32 elements.