Problem 3 - Campbell Biology

Question

The reactivity of an atom arises from (A) the average distance of the outermost electron shell from the nucleus. (B) the existence of unpaired electrons in the valence shells. (C) the sum of the potential energies of all the electron shells. (D) the potential energy of the valence shell.

Step-by-Step Solution

Answer

The answer is (B) the existence of unpaired electrons in the valence shells.

Step 1: Understand the Question

The exercise asks to determine the primary factor for an atom's reactivity. Key terms include 'reactivity' and 'valence shell'.

Step 2: Analyze the Options

Consider each option provided:(A) The average distance of the outermost electron shell from the nucleus.(B) The existence of unpaired electrons in the valence shells.(C) The sum of the potential energies of all the electron shells.(D) The potential energy of the valence shell.

Step 3: Evaluate Each Option

Option A: The average distance might affect reactivity but isn't the primary factor.Option B: Unpaired electrons in the valence shell contribute to an atom’s reactivity.Option C: Summing potential energies of all shells isn’t directly related to reactivity.Option D: The potential energy of the valence shell influences reactivity but isn't the main factor.

Step 4: Determine the Best Answer

Since the reactivity is primarily due to the presence of unpaired electrons in the valence shell, the best choice is (B).

Key Concepts

headline of the respective core concept

The reactivity of an atom is closely linked to several fundamental concepts in chemistry. Understanding these concepts can help you comprehend why certain atoms are more reactive than others. We'll dive into three key topics: valence electrons, electron configuration, and unpaired electrons. These elements all play essential roles in determining the behavior of atoms during chemical reactions.

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Valence electrons are the electrons found in the outermost shell of an atom. These electrons are crucial because they are the ones that participate in chemical reactions. Think of them as the 'social' electrons that interact with other atoms. For instance:

• Atoms with a full valence shell are typically less reactive because they are already stable.
• Atoms with one or more missing valence electrons tend to be more reactive as they seek to fill or empty their outer shell to achieve stability.

Elements in the same group of the periodic table have the same number of valence electrons, which explains their similar chemical properties. Therefore, understanding valence electrons can provide valuable insights into an element's reactivity and its position in the periodic table.

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Electron configuration refers to the arrangement of electrons in an atom. This configuration is essential because it determines how an atom will interact with others. An atom's electron configuration is expressed in terms of its energy levels and subshells, following the principles of quantum mechanics. For example:

• The Aufbau principle states that electrons occupy the lowest available energy orbitals first.
• The Pauli exclusion principle highlights that no two electrons can have the same set of quantum numbers, meaning an orbital can hold a maximum of two electrons with opposite spins.
• Hund's rule explains that electrons will fill unoccupied orbitals first before pairing up in the same orbital to minimize repulsion.

By understanding the electron configuration of an atom, you can predict its reactivity and the types of bonds it will form.

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Unpaired electrons are electrons that are alone in an orbital rather than paired with another electron. These unpaired electrons are highly significant in determining the reactivity of an atom. Here’s why:

• Atoms with one or more unpaired electrons tend to be more reactive because these electrons can easily participate in chemical reactions to form bonds.
• When atoms have unpaired electrons, they seek to pair them, either by sharing with another atom (covalent bonding) or by transferring electrons (ionic bonding).

For instance, halogens have high reactivity because they have one unpaired electron in their valence shell, making them eager to gain an electron to complete their outer shell. Therefore, the presence of unpaired electrons is a primary factor influencing an atom's reactivity, as highlighted in the original exercise.