Chapter 3, Problem 21A

Interpretation Introduction

Interpretation: The proton and neutron have exactly the same mass should be discussed.

Concept Introduction: Every matter is made of chemicals; the importance of chemistry is that it's the study of everything. Chemistry is all about how something interacts to affect the structure, composition, as well as knowing properties of substances.

Answer to Problem 21A

Both, Protons & neutrons, have approximately same mass. Protons are positively charged and neutrons have no charge. Protons and neutron both contribute majorly to the mass of atom because protons have positive charge and neutrons have negative charge.

Explanation of Solution

Protons are defined as a positively charged $\left(+ve\right)$ sub-atomic particles/ units found in the nucleus of an atom. Number of Protons present in an atom is known as atomic number. Atomic number is represented by symbol Z. Atomic number of an atom is the identity number of an element and the mass numbers are the number of electrons. Neutrons are subatomic particles found in the nucleus of an atom which are neutral.

Sum of number of protons and neutron in an atom is known as the mass number. Nucleon number is another number of mass number. The mass number is represented by the symbol A.

The proton & neutron have like, but not have identical, masses. Protons &neutrons are termed as nucleons as they are present in nucleus.

Mass of protons, $m_P=1.6726\times {10}^{-27}Kg$

Mass of neutrons, $m_N=1.6749\times {10}^{-27}Kg$

The combination of the protons and the neutrons makes up the bulk of the mass of the atom. Electrons have negative charge and protons have the positive charge. Both, contribute greatly to the chemical properties of atom.

Conclusion

The number of protons in an atom is termed as atomic number. Total number of protons and electrons are termed as mass number. By using the mass number and atomic number you can calculate the number of protons and neutrons.