During a manned mission to mars, astronaut mark watney is presumed dead after a fierce storm and left behind by his crew. but watney has survived and finds himself stranded and alone on the hostile planet. with only meager supplies, he must draw upon his ingenuity, wit and spirit to subsist and find a way to signal to earth that he is alive. if mark watney uses am waves (λ approximately 102 meters) to try and contact nasa, how long, in minutes, will it take for his message to reach earth from mars?

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

just did the assignment and the answer was #1 +2 n