Problem 10 - Chemistry The Central Science In Si Units

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. (b) Gain 2 electrons. (c) Gain 3 electrons.

Step 1: Understanding the hydrogen atom's electron stability

A hydrogen atom has one electron and can only have a maximum of two electrons in its valence shell, not a full octet. Therefore, statement (a) is false.

Step 2: Calculating electrons for sulfur to achieve an octet

Sulfur is in group 16 of the periodic table and naturally has six valence electrons. To achieve a full octet, it needs 8 electrons in total, so it must gain 2 electrons.

Step 3: Determining additional electrons for the given electron configuration

An atom with the electron configuration \(1s^2 2s^2 2p^3\) has a total of 5 valence electrons (in the second shell). To achieve an octet, it needs 8 electrons in its valence shell, so it must gain 3 additional electrons.

Key Concepts

Octet Rule

Atoms are most stable when they have complete outer electron shells. This idea is often referred to as the "Octet Rule" because, with a few exceptions, eight electrons in the valence shell provide stability. This rule is mainly applicable to main-group elements within the periodic table.

When atoms do not have a full octet naturally, they seek stability through chemical bonds. These bonds can be ionic or covalent, depending on whether electrons are transferred or shared.

It's important to note that there are exceptions to this rule, like hydrogen and helium, which only need two electrons to be stable—forming a "duet." Therefore, while the octet rule is a helpful guideline, it's not universally applicable. In context with the exercise, it's not suitable for hydrogen, which is most stable with just 2 electrons.

Valence Electrons

Valence electrons are the electrons located in the outermost electron shell of an atom. These electrons are crucial because they are the ones involved in chemical bonding.

The number of valence electrons determines the chemical reactivity of the element. Elements with a full set of valence electrons are generally inert. For example, noble gases, found in Group 18 of the periodic table, naturally have a full valence shell and are typically non-reactive.

Sulfur, mentioned in the exercise, belongs to Group 16 and for it to achieve an octet, it needs 2 more electrons, as it naturally has six. Acquiring these electrons can lead sulfur to form compounds such as sulfur dioxide or hydrogen sulfide.

Periodic Table Groups

Periodic Table Groups, or families, are columns within the periodic table that categorize elements based on similar chemical properties and valence electron configurations. Each group signifies the number of valence electrons its elements possess.

Elements in the same group have similar chemical properties because they have the same number of electrons in their outermost shell. For example:

• Group 1: Alkali metals, with one valence electron
• Group 17: Halogens, with seven valence electrons
• Group 18: Noble gases, with a full valence shell

Understanding these groups can help predict how different elements will react chemically. From the exercise, sulfur is in Group 16, which has six valence electrons, often resulting in the need to gain electrons to comply with the octet rule.