Define the following:
a. atomic number
b. mass number
c. isotope
The correct answer and explanation is:
a. Atomic number:
The atomic number is the number of protons in the nucleus of an atom. It defines the identity of an element and determines its position in the periodic table. For example, the atomic number of hydrogen is 1, meaning it has one proton in its nucleus. The atomic number also indicates the number of electrons in a neutral atom, as the number of protons equals the number of electrons.
b. Mass number:
The mass number is the total number of protons and neutrons in an atom’s nucleus. It gives an approximate mass of the atom in atomic mass units. For example, if an atom has 6 protons and 6 neutrons, its mass number is 12. The mass number does not account for electrons, as their mass is negligible compared to protons and neutrons. This number is useful in distinguishing between different isotopes of an element.
c. Isotope:
An isotope is a variant of an element that has the same atomic number but a different mass number. This means isotopes of the same element have the same number of protons but a different number of neutrons. For example, carbon-12 and carbon-14 are isotopes of carbon. Both have 6 protons but differ in the number of neutrons—carbon-12 has 6 neutrons, while carbon-14 has 8 neutrons. Isotopes of an element have similar chemical properties but may have different physical properties, such as stability. Some isotopes are radioactive and decay over time, emitting radiation in the process.
In summary, the atomic number defines the identity of an element and its electron configuration, the mass number gives the sum of protons and neutrons in an atom, and isotopes are variations of the same element differing in neutron count and mass number.