Which of the following does not accurately describe transistors?
a. both npn and pnp transistors consist of a base composed of an n-type material.
b. both npn and pnp transistors consist of p-type and n-type material.
c. both npn and pnp transistors operate in the same manner but with interchanged terminals and opposite directions of voltage and current.
d. both npn and pnp transistors consist of an emitter, base, and collector.

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.  

fe 55.85 g/mol and h2o 18.02 g/mol.