The valency of chlorine atom is________and this value is taken as the standard value.

The valency of a chlorine atom is typically considered to be 1. This value is widely accepted as the standard because it reflects chlorine's tendency to gain or share one electron in chemical reactions, allowing it to achieve a stable electronic configuration similar to that of noble gases.

Understanding Valency in Chemistry

Valency refers to the ability of an atom to bond with other atoms, which is determined by the number of electrons in its outermost shell. For chlorine, which has an atomic number of 17, the electron configuration is 2, 8, 7. This means it has seven electrons in its outer shell and needs one more to complete the octet rule, which states that atoms are most stable when they have eight electrons in their outer shell.

Chlorine's Chemical Behavior

Chlorine is a halogen, located in Group 17 of the periodic table. Its high electronegativity indicates a strong tendency to attract electrons. When chlorine reacts with other elements, it often forms compounds by either gaining an electron to become a negatively charged ion (Cl⁻) or sharing an electron in covalent bonds. This behavior is what gives chlorine its valency of 1.

Examples of Chlorine's Valency in Action

• Formation of Sodium Chloride (NaCl): In this common table salt, sodium (Na) donates one electron to chlorine, allowing chlorine to achieve a full outer shell. Here, chlorine's valency of 1 is evident as it accepts one electron.
• Covalent Bonding in Chlorine Gas (Cl₂): When two chlorine atoms bond together, they share one pair of electrons. Each chlorine atom effectively has a valency of 1, as they each contribute one electron to the bond.

Why Valency Matters

Understanding the valency of elements like chlorine is crucial in predicting how they will interact with other elements. It helps chemists formulate compounds and understand the properties of substances. For instance, knowing that chlorine has a valency of 1 allows for the anticipation of its behavior in reactions, such as its role in disinfectants or its use in the production of various chemicals.

In summary, the standard valency of chlorine is 1, reflecting its chemical behavior and its tendency to form bonds that allow it to achieve a stable electron configuration. This foundational concept is essential for grasping more complex chemical interactions and reactions.