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The image shows the representation of an unknown element in the periodic table.

A square is shown. Inside the square nine is written at the top righthand side. To the middle left side, Symbol is written. Below it Name is written. And further below near the bottom edge of the square, eighteen point nine nine eight four is written.

Based on the representation, which of the following statements about the element is true?

The combined number of protons plus electrons is 9.
The number of neutrons in an atom of the element is 10.
The combined mass of neutrons and electrons is 18.9984.
The sum of the masses of protons and electrons is 18.9984.

1 answer

Based on the information provided in the representation of the unknown element, we can analyze the details:

  1. The number "nine" in the upper right corner usually represents the atomic number, which is the number of protons in an atom. Therefore, the element has 9 protons.

  2. Since the element is neutral (which is typically implied unless otherwise stated), it will also have 9 electrons.

  3. The atomic mass (given as 18.9984) typically reflects the total mass of an atom, primarily contributed by protons and neutrons (with a minor contribution from electrons, which is negligible because their mass is very small).

Now let's evaluate the statements:

  1. The combined number of protons plus electrons is 9.

    • This statement is false. Protons + electrons = 9 + 9 = 18.

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

    • The atomic mass is approximately 19. Since atomic mass = protons + neutrons, we can derive: \[ 19 = 9 + \text{neutrons} \] \[ \text{neutrons} = 19 - 9 = 10 \]
    • This statement is true.

  3. The combined mass of neutrons and electrons is 18.9984.

    • This is false. The mass of electrons is negligible compared to that of neutrons and protons, so the statement doesn’t hold.

  4. The sum of the masses of protons and electrons is 18.9984.

    • This is also false, since the mass contributions of the protons can be approximated from the atomic mass, and we know protons significantly outweigh electrons in mass.

Thus, the only true statement from the options provided is:

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