Question

which statement is true about all the atoms of a given element?
a they all have the same number of protons.
b they can have a different number of protons.
c they have the same number of neutrons.
d they are the same size as the atoms of all other elements.

Explanation:

Atoms of a given element can have different numbers of neutrons (isotopes), but always the same number of protons. Option a is incorrect as they don't all have the same number of protons (that's for same - element atoms). Option c is wrong because neutrons can vary (isotopes). Option d is incorrect as atom size varies by element. Option b is correct as isotopes (atoms of the same element) can have different neutron numbers (thus different mass numbers while protons are same).

Answer:

B. They can have a different number of protons.