Question

How many protons, neutrons, and electrons are there in one atom of hafnium-178?

A. 72 protons, 106 neutrons, 72 electrons
B. 89 protons, 178 neutrons, 89 electrons
C. 108 protons, 70 neutrons, 70 electrons
D. 70 protons, 108 neutrons, 70 electrons
E. 89 protons, 89 neutrons, 178 electrons

Answer 1

An atom of hafnium-178 has 72 protons, 106 neutrons, and 72 electrons, since Hafnium has an atomic number of 72 and a mass number of 178.

Step-by-step explanation:

To determine the number of protons, neutrons, and electrons in an atom of hafnium-178 (Hf-178), we need to look at its atomic number and its mass number. The atomic number gives us the number of protons and, because atoms are electrically neutral, also the number of electrons. The mass number provides the total number of protons and neutrons in the nucleus.

Hafnium has an atomic number of 72, which means it has 72 protons and, in its neutral state, 72 electrons. The mass number of Hafnium-178 means it has a total of 178 protons and neutrons combined. Subtracting the number of protons (72) from the mass number (178) gives us the number of neutrons, which is 178 - 72 = 106 neutrons.

Therefore, the correct answer is A. 72 protons, 106 neutrons, 72 electrons.