Define mono-valent, divalent and trivalent elements with example.

In chemistry, elements can be classified based on the number of electrons they can lose, gain, or share when forming chemical bonds. This classification leads us to terms like mono-valent, divalent, and trivalent elements. Let’s break these down one by one, along with examples to clarify their meanings.

Mono-valent Elements

Mono-valent elements are those that have a valency of one. This means they can form one bond by either losing one electron or gaining one electron. A common example of a mono-valent element is sodium (Na). Sodium has one electron in its outermost shell, and when it loses that electron, it achieves a stable electronic configuration similar to that of noble gases. This is why sodium typically forms a +1 ion (Na⁺).

Characteristics of Mono-valent Elements

• Typically found in Group 1 of the periodic table.
• Form ionic compounds with non-metals.
• Examples include potassium (K) and lithium (Li).

Divalent Elements

Divalent elements possess a valency of two, meaning they can form two bonds. This can occur through the loss of two electrons or the gain of two electrons. A prime example of a divalent element is magnesium (Mg). Magnesium has two electrons in its outer shell, and when it loses both, it forms a +2 ion (Mg²⁺), which is commonly found in compounds like magnesium oxide (MgO).

Features of Divalent Elements

• Located in Group 2 of the periodic table.
• Often form ionic bonds with non-metals.
• Other examples include calcium (Ca) and barium (Ba).

Trivalent Elements

Trivalent elements have a valency of three, allowing them to form three bonds. They can achieve this by losing three electrons or gaining three electrons. Aluminum (Al) is a well-known trivalent element. It has three electrons in its outer shell, and when it loses these electrons, it forms a +3 ion (Al³⁺), which is prevalent in compounds like aluminum oxide (Al₂O₃).

Properties of Trivalent Elements

• Found in Group 13 of the periodic table.
• Can form both ionic and covalent bonds.
• Other examples include gallium (Ga) and indium (In).

Summary of Valency

To summarize, the valency of an element determines how it interacts with other elements in chemical reactions. Mono-valent elements like sodium form one bond, divalent elements like magnesium form two bonds, and trivalent elements like aluminum form three bonds. Understanding these classifications helps in predicting the behavior of elements in various chemical contexts.