Question

the atomic number of an atom equals the number of ___ and the atomic weight equals the ___.
a neutrons; number of protons
b protons; weight of all the electrons
c neutrons; number of protons plus electrons
d protons; number of protons plus neutrons

question 18
the atomic weight of an element whose atoms contain 8 protons, 8 electrons, and 8 neutrons is
a 8.
b 16.
c 24.
d 32.

Explanation:

First Question (Atomic Number and Atomic Weight)

To solve this, we recall atomic structure concepts:

• Atomic number is the number of protons in an atom (electrons equal protons in neutral atoms, but atomic number is defined by protons).
• Atomic weight (mass number) is the sum of protons and neutrons (electrons have negligible mass).

Now analyze options:

• Option A: Atomic number ≠ neutrons, atomic weight ≠ protons. Eliminate.
• Option B: Atomic weight ≠ electron weight (electrons are negligible). Eliminate.
• Option C: Atomic number ≠ neutrons, atomic weight ≠ protons + electrons. Eliminate.
• Option D: Atomic number = protons, atomic weight = protons + neutrons. Correct.

Step1: Recall atomic weight formula

Atomic weight (mass number) = number of protons + number of neutrons (electrons’ mass is negligible).

Step2: Substitute values

Protons = 8, Neutrons = 8.
Atomic weight = \( 8 + 8 = 16 \).

Answer:

D. protons; number of protons plus neutrons

Question 18 (Atomic Weight Calculation)