At the top of a roller coaster you have 90j of potential energy and 10 j of kinetic energy at the bottom of the roller coaster you now have 90j of kinetic energy how much potential energy do you have at the bottom of the coaster?

The energy has to be conserved thus the final energy level will always be equal to the initial state .. the initial state has 90j of potential energy and 10j of kinetic energy the total energy is equal to = 100j .

now for the second condition the kinetic energy is 90j and the total energy is 100j thus 100j-90j = 10j of potential energy

It won't lose or gain electrons if it's a covalent bond it shares the electrons with another atom or atoms. if it is an ionic bond it will lose the 3 electrons on the outer shell and become a positively charged ion.  credit goes to @sunshinebaby of answers.yahoo.com.