Question

Alkali metals present in their compounds are always: (a) Monovalent (b) Bivalent (c) Zerovalent (d) None of these

Short answer

Alkali metals are monovalent (Option a).

Step-by-step solution

Understand Alkali Metals

Alkali metals are found in Group 1 of the periodic table. This group includes elements such as lithium, sodium, and potassium.

Determine Valence Electrons

Alkali metals have a single electron in their outermost shell. This is the characteristic electron configuration for elements in Group 1.

Determine Common Oxidation State

In chemical reactions, alkali metals typically lose their one valence electron to form a cation with a charge of +1. This makes them monovalent.

Evaluate Options

Based on their properties, alkali metals are monovalent as they form ions with a +1 charge. Option (a) is the correct choice for representing their valency in compounds.

Key concepts

Monovalency

Alkali metals are known for their monovalency, which means they form ions with a single positive charge, or +1. This property arises because these metals possess one electron in their outermost shell. Losing this electron fulfills the metal's tendency to reach a stable electron configuration, akin to the nearest noble gas.
For instance:

• Lithium (Li) loses its one outer electron to become Li⁺.
• Sodium (Na) becomes Na⁺ after losing its single valence electron.
• Potassium (K) transforms to K⁺ upon losing the outer electron.

This feature is a hallmark of alkali metals, confirmed by their consistent formation of +1 ions in chemical reactions.

Valence Electrons

Valence electrons are the outermost electrons of an atom, and they play a crucial role in chemical bonding. For alkali metals, there is just one valence electron located in their outer shell.
This single electron sets alkali metals apart in Group 1 of the periodic table. These valence electrons are responsible for the chemical reactivity of alkali metals. As they are eager to lose this lone electron to achieve the stability of a full outer shell, alkali metals exhibit high reactivity, especially with halogens and water.
Understanding this concept is key to grasping why alkali metals readily form monovalent cations in reactions.

Oxidation States

The oxidation state, often called oxidation number, refers to the degree of oxidation of an atom in a chemical compound. For alkali metals, this is consistently +1, which highlights their tendency to lose one electron during reactions.
This consistent +1 oxidation state of alkali metals contributes to their simplicity in chemical behavior. They readily engage in ionic bonding, where they donate their one valence electron to nonmetals, usually resulting in the formation of salts.
Recognizing this stable oxidation state helps predict the behavior and products of alkali metals in reactions, emphasizing their predictability in forming compounds.

Group 1 Elements

Group 1 elements, known as alkali metals, are located in the first column of the periodic table. They include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). These elements share similar physical and chemical properties due to their structural characteristics.
Key features of Group 1 elements include:

• Softness and low density, with lithium being the lightest metal.
• High reactivity, especially with water, forming hydroxides and releasing hydrogen gas.
• Low ionization energies, making them highly reactive.
• Consistency in forming +1 ions in solutions, emphasizing their monovalency.

Understanding these properties gives insight into the behavior and applications of alkali metals in various fields, from industrial uses to chemical synthesis processes.