Which statement correctly describes a physical change?

a) involves breaking and creating chemical bonds but not changing a phase

b) may involve a change in phase but does not involve a change in the molecular structure

c) may involve converting two or more substances into new substances

d) involves changes at the molecular level

e) involves energy transfer and change in color

The statement that correctly describes a physical change is may involve a change in phase but does not involve a change in the molecular structure. The answer is letter B.

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.