Atomic Structure of Gold Isotope Au-197

How many protons, neutrons, and electrons are in an atom of the most common isotope of gold, 197 Au?

A) 79, 118, 118

B) 79, 197, 197

C) 79, 118, 79

D) 118, 79, 39

E) 197, 79, 118

Answer:

An atom of the most common isotope of gold, 197 Au, has 79 protons, 118 neutrons, and 79 electrons. Therefore, the correct answer is C) 79, 118, 79.

An atom of the most common isotope of gold, 197 Au, has 79 protons, 118 neutrons, and 79 electrons. This is because the atomic number of gold, which indicates the number of protons in the nucleus, is 79. The mass number of the isotope is the sum of its protons and neutrons, which is 197 (79 protons + 118 neutrons). Since atoms are electrically neutral, the number of electrons equals the number of protons.

Gold is a unique element in that 100% of the gold found naturally is in the form of the isotope Au-197. There are 28 other isotopes of gold that can be produced artificially, and they are all radioactive. Gold, along with silver and copper, forms a column in the periodic table. These three elements are found naturally and were the first three elements known to man.