Question

use the periodic table and observe the element with a mass of 35. if the atomic mass number of an atom is 35, which statement is most accurate?
a the atomic number is less than 16.
b the atomic number is over 35.
c the number of protons does not equal the number of neutrons.
d the atom has 20 neutrons.

Explanation:

Step1: Recall the relationship between atomic mass, atomic number, protons, and neutrons

Atomic mass \(A\) = number of protons \(p\) + number of neutrons \(n\). Atomic number \(Z\) = number of protons \(p\).

Step2: Analyze option A

If atomic number \(Z<16\), then \(p < 16\). If \(A = 35\), then \(n=A - p>35 - 16=19\). But we have no information to support \(Z<16\) just from \(A = 35\).

Step3: Analyze option B

If \(Z>35\), then \(p>35\). But \(A=p + n=35\), so \(n=35 - p<0\), which is impossible.

Step4: Analyze option C

Since \(A=p + n\), and \(A = 35\). Protons and neutrons are not necessarily equal. For example, if \(p = 17\), \(n = 18\) (as in \(^{35}\text{Cl}\), where \(Z = 17\), \(A=35\), \(n=35 - 17 = 18\)). So the number of protons does not equal the number of neutrons.

Step5: Analyze option D

We know \(A=p + n=35\). If we assume \(p = 17\) (as in chlorine - 35), \(n=35 - 17=18
eq20\). There is no basis to say \(n = 20\) from \(A = 35\) alone.

Answer:

C. The number of protons does not equal the number of neutrons.