this is how sodium appears in the periodic table. the arrow pointing to sodium’s

The arrow is pointing to sodium's combined number of neutrons and protons.

Explanation:

The mass number or atomic mass represents the number of protons and neutrons found within the nucleus of the atom. That is, the sum of the protons and neutrons present in the nucleus of an atom, gives us the mass number. It is symbolized with the letter A.

The isotopes of an element are those in which their atomic numbers (that is, the number of protons) are equal, but the number of neutrons is different, that is, the mass number varies. The same chemical element may consist of different atoms, that is, different isotopes. Then the atomic mass of an element is the weighted average mass of its natural isotopes. Therefore, the atomic mass of an element is not an integer. The weighted average means that not all isotopes have the same percentage. In other words, the atomic masses of the chemical elements are usually calculated as the weighted average of the masses of the different isotopes of each element taking into account the relative abundance of each of them. The atomic mass of an element (also known as atomic weight) is the average mass of atoms of an element. The atomic mass can be found below the symbol of the element.

Knowing that the mass number is indicative of the different isotopes of a chemical element (where the number of protons is identical for all atoms of the element, and the number of neutrons in the nucleus varies, thus changing the mass number, and indicating of what isotope of the element is) and considering that the atomic mass of an element is the average mass of the different elements of an element, it is possible to say that the atomic mass of the element house indicates the sum of neutrons and protons present in the nucleus of the atom.

Finally, the arrow is pointing to sodium's combined number of neutrons and protons.

D. combined number of electrons and protons.

Hope this helps

-Amelia

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: