Question

question 18 (1 point)
(02.02 mc)
the image shows the representation of an unknown element in the periodic table.
based on the representation, which of the following statements about the element is true?
a the total number of protons plus electrons is 10.
b the number of neutrons in an atom of the element is 20.
c the sum of the masses of protons and neutrons is 20.1797.
d the mass of only the protons in the nucleus is 20.1797.

Explanation:

Step1: Identify atomic number and atomic mass

The number 10 is the atomic number. Atomic number = number of protons. In a neutral atom, number of protons = number of electrons. So number of protons = 10 and number of electrons = 10. The number 20.1797 is the atomic - mass (average mass of all isotopes of the element).

Step2: Analyze option a

The total number of protons plus electrons is \(10 + 10=20\), not 10. So option a is false.

Step3: Analyze option b

Atomic mass is approximately the sum of protons and neutrons. If atomic number (number of protons) is 10 and atomic mass is 20.1797, the number of neutrons is approximately \(20.1797 - 10\approx10\) (since protons and neutrons each have a mass of about 1 amu), not 20. So option b is false.

Step4: Analyze option c

The atomic mass (20.1797) is the sum of the masses of protons and neutrons (taking into account the relative abundances of isotopes). So option c is true.

Step5: Analyze option d

The mass of only the protons is not 20.1797. The atomic mass includes the mass of both protons and neutrons. So option d is false.

Answer:

c