CAMPBELL BIOLOGY IN FOCUS-MOD.MASTERING
CAMPBELL BIOLOGY IN FOCUS-MOD.MASTERING
3rd Edition
ISBN: 9780135191811
Author: Urry
Publisher: PEARSON
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Chapter 2, Problem 1TYU

The reactivity of an atom arises from

  1. A.    the average distance of the outermost electron shell from the nucleus.
  2. B.     the existence of unpaired electrons in the valence shell.
  3. C.     the sum of the potential energies of all the electron shells.
  4. D.    the potential energy of the valence shall.
Expert Solution & Answer
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Summary Introduction

Introduction:

An atom is the smallest possible particle of an element. It is the basic unit of any structure found in the universe. Two or more atoms together make a molecule.

Answer to Problem 1TYU

Correct answer:

The reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

Therefore, option (B) is correct.

Explanation of Solution

Reason for the correct statement:

Unpaired electrons in a valence shell are unstable in nature and in order to become stable, an atom can lose or gain electrons and becomes reactive.

Option (B) is given as “the existence of unpaired electrons in the valence shell”.

As “the reactivity of an atom arises from the existence of unpaired electrons in the valence shell”, it is the right answer.

Hence, option (B) is correct.

Reasons for the incorrect statements:

Option (A) is given as “the average distance of the outermost electron shell from the nucleus”.

If the distance of the outermost electron shell is large, then there would be a lesser nuclear effective charge. Thus, an electron can easily be expelled out of its shell. Thus, it does not cause an atomic reactivity. Hence, it is the wrong answer.

Option (C) is given as “the sum of the potential energies of all the electron shells”.

The sum of the potential energies of all the electron shells affects only the chemical properties of the atom and is not involved in its reactivity. Hence, it is the wrong answer.

Option (D) is given as “the potential energies of the valence shell”.

The potential energy of the valence shell decides which shell would get the electron first and is not involved in its reactivity. Hence, it is the wrong answer.

Hence, options (A), (C), and (D) are incorrect.

Conclusion

The number of electrons present in the outermost shell of an atom determines the atom reactivity.

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CAMPBELL BIOLOGY IN FOCUS-MOD.MASTERING

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