Problem 10 - Chemistry: The Central Science in SI Units, Global Edition

Question

(a) True or false: The hydrogen atom is most stable when it has a full octet of electrons. (b) How many electrons must a sulfur atom gain to achieve an octet in its valence shell? (c) If an atom has the electron configuration \(1 s^{2} 2 s^{2} 2 p^{3},\) how many electrons must it gain to achieve an octet?

Step-by-Step Solution

Answer

(a) False: The hydrogen atom requires only 2 electrons to have a stable configuration, not a full octet of electrons. (b) Sulfur, with 6 valence electrons, must gain 2 more electrons to achieve an octet in its valence shell. (c) With the given electron configuration \(1s^2 2s^2 2p^3\), the atom must gain 3 more electrons to achieve an octet in its valence shell.

Step 1: Part A: True or False

The hydrogen atom has only one electron orbiting around its nucleus in the 1s orbital. The maximum number of electrons that can fill the first shell (1s orbital) is 2, so hydrogen only requires 2 electrons to have a stable configuration. In this case, an octet (8 electrons) is not possible for hydrogen, so the statement is false.

Step 2: Part B: Sulfur Octet

Sulfur is in Group 16 (or Group 6A) of the periodic table. Consequently, it has 6 valence electrons in its outer shell. To achieve an octet (8 electrons), sulfur must gain 2 more electrons to complete its valence shell.

Step 3: Part C: Electron Configuration Octet

The given electron configuration is \(1s^2 2s^2 2p^3\). In order to calculate the number of electrons it must gain to achieve an octet, we start by looking at the last number in the configuration, which represents the number of valence electrons in the outermost shell. In this case, the valence shell (second shell) has a total of \(2 + 3 = 5\) electrons: 2 electrons in the 2s subshell and 3 electrons in the 2p subshell. To achieve an octet, it needs to gain 3 more electrons to complete the valence shell, making it a total of 8 electrons in the outer shell.

Key Concepts

Electron Configuration

Electron configuration is like a detailed map of an atom's electrons. Each electron in an atom occupies a specific shell and subshell, which are arranged according to increasing energy levels.
For example, the electron configuration \(1s^2 2s^2 2p^3\) describes an atom with seven electrons.

• The "1s" refers to the first shell (closest to the nucleus) and its s subshell, with a capacity of 2 electrons.
• "2s" and "2p" refer to the second shell, with the 2s subshell holding 2 electrons, and 2p holding 3 electrons.

Understanding electron configurations helps to predict an atom's chemical behavior and reactivity. It reveals the distribution of electrons and identifies how many electrons need to be added or removed to achieve stability, particularly regarding the octet rule.

Valence Electrons

Valence electrons are the outermost electrons that determine an atom's ability to bond with other atoms. These electrons are key players in chemical reactions and are found in the outermost shell of an atom.
Atoms aim to fill their outer shell to achieve stability, often striving for an octet configuration.
For instance, sulfur, located in Group 16 of the periodic table, has 6 valence electrons. To achieve an octet, it requires 2 more electrons. Atoms with fewer than 8 valence electrons will generally seek to gain, lose, or share electrons to complete their octet, forming ions or molecules through bonds.

• Valence electrons are crucial for chemical bonding.
• They decide how atoms interact, forming compounds and molecules.

Understanding the concept of valence electrons is essential for grasping chemical bonding and the reactivity of elements.

Periodic Table Groups

The periodic table is organized into groups (vertical columns) and periods (horizontal rows). Groups are particularly significant because they tell us about the elements' similar chemical properties and the number of valence electrons.
Elements in the same group tend to exhibit similar reactivity and chemical behavior.
For example:

• Group 1 elements (alkali metals) each have 1 valence electron and are highly reactive.
• Group 18 elements (noble gases) have full outer shells, rendering them very stable and mostly inert.

Sulfur, as a member of Group 16, shares similar traits with oxygen and selenium, such as having 6 valence electrons. Understanding periodic table groups allows us to predict how different elements will interact with each other. This organization gives important clues about electron configuration and chemical behavior across the table.