Question

How many protons (p) and neutrons (n) are in an atom of ^227_89 Ac? a)138 p, 89 n b)89 p, 138 n c)227 p, 89 n d)89 p, 227 n

Answer 1

An atom of ^227_89 Ac (Actinium) contains 89 protons and 138 neutrons. The atomic number provides the proton count and subtracting the atomic number from the mass number yields the neutron count. So, the correct option is B.

Step-by-step explanation:

An atom of ^227_89 Ac (Actinium) has an atomic number of 89 and a mass number of 227. The atomic number represents the number of protons in the nucleus, which also equals the number of electrons in a neutral atom. Therefore, this atom has 89 protons. The mass number is the sum of protons and neutrons in the nucleus. To find the number of neutrons, subtract the atomic number from the mass number: 227 (mass number) - 89 (atomic number) = 138 neutrons. Hence, the correct answer to the student's question is 89 protons and 138 neutrons (b).