Question

question 19 (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 combined number of protons plus electrons is 9. b the number of neutrons in an atom of the element is 10. c the combined mass of neutrons and electrons is 18.9984. d the sum of the masses of protons and electrons is 18.9984.

Explanation:

Step1: Identify atomic number and atomic mass

The atomic number is 9, which means the number of protons is 9. The atomic mass is 18.9984.

Step2: Calculate number of neutrons

The number of neutrons = atomic mass - number of protons. Rounding 18.9984 to 19, number of neutrons = 19 - 9=10.

Step3: Analyze electron - proton relationship

In a neutral atom, the number of electrons equals the number of protons. Here, number of protons = 9, so number of electrons = 9. The combined number of protons and electrons is 9 + 9=18, not 9.

Step4: Consider mass contributions

The mass of electrons is negligible compared to protons and neutrons. The atomic mass is mainly due to protons and neutrons.

Answer:

B. The number of neutrons in an atom of the element is 10.