2. sc 8.p.8.1
an artist heats a solid iron rod and bends it into a new shape. the iron cools down when the artist is
finished. what happens to the iron atoms as the solid iron rod cools?
a. the iron atoms move more quickly.
b. the iron atoms slow down and stop moving.
c. the iron atoms slow down and vibrate in place.
d. the speed of the iron atoms does not change.

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.  

the answer is d.) potassium