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Chapter 2: Problem 25

(a) Define atomic number and mass number. (b) Which of these can vary without changing the identity of the element?

Short Answer

Expert verified
(a) Atomic number (\(Z\)) is the number of protons in the nucleus of an atom, uniquely identifying an element. Mass number (\(A\)) is the total number of protons and neutrons in the nucleus. (b) The mass number can vary without changing the element's identity, as variations in neutron quantity form different isotopes of the same element.

Step by step solution

01

Part (a): Define Atomic Number and Mass Number

Atomic number is the number of protons in the nucleus of an atom. It is represented by the symbol \(Z\). The atomic number uniquely identifies an element, since no two elements have the same number of protons. Mass number, also known as nucleon number, is the total number of protons and neutrons in the nucleus of an atom. It is represented by the symbol \(A\). The mass number is not unique to an element, as isotopes of the same element can have different mass numbers due to the varying number of neutrons.
02

Part (b): Determination of Variation

Between atomic number and mass number, the one that can vary without changing the identity of the element is the mass number. This is because the mass number takes into account both protons and neutrons within the nucleus of an atom. The number of neutrons can vary in an element, giving rise to different isotopes, but the number of protons (i.e., the atomic number) remains constant for a particular element. Changing the number of protons would result in a different element altogether.

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Most popular questions from this chapter

Provide the name or chemical formula, as appropriate, for each of the following acids: (a) hydroiodic acid, (b) chloric acid, \((\mathbf{c})\) nitrous acid, $(\mathbf{d}) \mathrm{H}_{2} \mathrm{CO}_{3},(\mathbf{e}) \mathrm{HClO}_{4},\( (f) \)\mathrm{CH}_{3} \mathrm{COOH}$.

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