Question

Argon and Calcium both have an atomic mass that rounds to 40, but they have different atomic numbers. What are the differences between the two atoms, based on the information given?


Argon has more neutrons, but Calcium has more protons.


Argon and Calcium have a different number of protons, but the same number of electrons when neutrally charged.


Argon and Calcium have the same number of neutrons, but they have a different number of protons.


Argon has more proton, but Calcium has more neutrons.


Argon and Calcium have the same number of protons, but they have a different number of neutrons.

Answer 1

The correct answer is: Argon has more neutrons, but Calcium has more protons.

The atomic number is the number of protons in an atom. In this case, argon has 18 protons and calcium 20.

The atomic mass (mass number) of an element is determined by the number of protons and the number of neutrons.

This means that the number of neutrons is atomic mass-atomic number. So, argon has 40-18=22 and calcium 40-20=20 neutrons.

Answer 2

The difference between the two Atoms

Calcium and argon have the same atomic mass but have a different atomic mass because the atomic number depends upon a number of protons which is mainly different. Argon has 18 number of protons which is its atomic number and calcium has 20 number of protons. A number of neutrons and protons are different. But atomic mass (A=Z+n)  is the same. Atomic mass is the sum of the atomic number number of protons and number of neutrons.