Question

how many neutrons are present in a bromine atom with a mass number of 81?
35
24
81
46
question 10
1 pts
the atomic mass number of an atom comprised of 6 protons, 6 neutrons and 6 electrons is ______.
24 amu
18 amu
12 amu
6 amu

Explanation:

Step1: Recall bromine's atomic number

Bromine's atomic number is 35, which means it has 35 protons.

Step2: Use mass - number formula

The mass number (A) = number of protons (p) + number of neutrons (n). Given A = 81 and p = 35, we can find n. Rearranging the formula gives n=A - p. So n = 81 - 35 = 46.

Step3: Recall atomic mass number formula for second question

The atomic mass number (A) is the sum of protons and neutrons. Given 6 protons and 6 neutrons, A=6 + 6=12. Electrons do not contribute to the mass number.

Answer:

For the first question: D. 46
For the second question: C. 12 amu