A J-shaped tube, closed at one end, is depicted in the figure at the right. It contains N2 gas that is trapped by an unknown liquid whose density is twice as large as that of mercury. The other end of the tube is open to the air. The value of h is measured to be 10 mm at sea level on a clear day at a temperature of 27°C. The atmospheric pressure is 1.00 atm. Assuming the vapor pressure of the liquid is zero, what is the concentration of the N2 gas trapped inside the J-shaped tube?

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.