What is the atomic number of Tin?

What is the atomic number of Tin?

• A. 22
• B. 8
• C. 80
• D. 50

Answer: (D)

The main idea is that the atomic number equals the number of protons in an atom’s nucleus, and this number uniquely identifies the element. Tin has 50 protons, so its atomic number is 50. In a neutral atom, the same number of electrons balance that, so tin would have 50 electrons as well. The other numbers point to different elements—22 corresponds to titanium, 8 to oxygen, and 80 to mercury—so they don’t describe tin.

The main idea is that the atomic number equals the number of protons in an atom’s nucleus, and this number uniquely identifies the element. Tin has 50 protons, so its atomic number is 50. In a neutral atom, the same number of electrons balance that, so tin would have 50 electrons as well. The other numbers point to different elements—22 corresponds to titanium, 8 to oxygen, and 80 to mercury—so they don’t describe tin.