He 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

Option (b) is the correct answer.

Explanation:

Atomic number is the sum of total number of protons present in an atom. And, atomic mass is the sum of total number of protons and neutrons present in an element.

Also, in a neutral atom the number of protons equal to the number of electrons.

Generally, atomic number is written on the top right corner of the symbol of an element and atomic mass is written at the bottom.

So here, number 9 is the atomic number and its atomic mass will be approximately 19.

Therefore, number of neutrons present in the given element will be as follows.

                    Atomic mass = no. of protons + no. of neutrons

                              19 = 9 + no. of neutrons

                        no. of neutrons = 19 - 9

                                                 = 10

Thus, we can conclude that the statement number of neutrons in an atom of the element is 10, is true.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.