Answer:
to find the number of electrons you need the charge of the element.
Trace fossils provide us with indirect evidence of life in the past, such as the footprints, tracks, burrows, borings, and feces left behind by animals, rather than the preserved remains of the body of the actual animal itself. so i would say B.
Standard temperature is 273 K
Standard pressure is 1 atm
We use the ideal gas equation to find out density of nitrogen gas in g/L
Ideal gas equation:

Molar mass of 
Pressure = 1 atm
Temperature = 273 K

= 1.25 g/L
Therefore, density of nitrogen gas at STP is 1.25 g/L
Answer:
Oxygen is limiting reactant
Explanation:
2 H2 + O2 ======> 2 H2 O
from this equation (and periodic table) you can see that
4 gm of H combine with 32 gm O2
H / O = 4/32 = 1/8
32 /16 = 2/1 shows O is limiter
for 32 gm H you will need 256 gm O and you only have 16 gm