How many protons, neutrons and electrons are present in an atom of hafnium, hf, with a mass number of 178?

72 protons

102 neutrons

72 electrons

Explanation:

Hf has an atomic number of 72. By definition, this means that it has 72 protons.

It also has a mass number of 178. The mass number (A) counts all elements with significant mass (protons and neutrons). Then,

A = p⁺ + n⁰

n⁰ = A - p⁺ = 178 - 72 = 102

Hf has 102 neutrons.

Elemental Hafnium is electrically neutral because it has the same amount of  positive charges (protons) and negative charges (electrons). Then, it must have 72 electrons.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

answer; the numbers of valence electrons in the acetic acid molecule (ch3co2h) is 24;