Question

the ion $^{75}as^{- 3}$ contains (as is element 33, you should have a copy of the periodic table)

1 protons
2 neutrons
3 electrons
4 nucleons

a. 75 b. 3 c. 33 d. 34 e. 35 f. 36 g. 37
h. 30 i. 40 j. 42 k. 39 l. 45 m. 78 n. 72

Explanation:

Step1: Determine number of protons

The atomic number of As is 33, and the number of protons is equal to the atomic number. So, the number of protons is 33.

Step2: Calculate number of neutrons

The mass - number is 75. The number of neutrons = mass - number - number of protons. So, 75 - 33=42.

Step3: Calculate number of electrons

The ion is $As^{- 3}$, which means it has gained 3 electrons. A neutral As atom has 33 electrons. So, the number of electrons in $As^{-3}$ is 33 + 3=36.

Step4: Determine number of nucleons

Nucleons are protons + neutrons. So, 33+42 = 75.

Answer:

1. C. 33
2. J. 42
3. F. 36
4. A. 75