The # 4 is the only significant # in 400.. Trailing 0's r not significant unless there is a decimal.
in 0.7000, there are 4 significant #'s.
<span>B. 51 50
Z and Z
25 25
It is because only this element have equal number of Protons (Bottom number) and are different in atomic masses (upper number)
Hope this helps!</span>
The third one down: "When barium hydroxide is mixed with ammonium chloride, ice crystals form on the outside of the container."
This is because an endothermic reaction [process] takes in more energy than it releases. Therefore because a decrease in energy leads to a decrease in temperature, the ice crystals forming show that it must be a endothermic reaction [process].
Hope this helps! :)
AJ
