Identify the incorrect statement from the following
- Alkali metals react with water to form their hydroxides
- The oxidation number of K in KO2 is +4.
- Ionisation enthalpy of alkali metals decreases from top to bottom in the group.
- Lithium is the strongest reducing agent among the alkali metals.
The Correct Option is B
Solution and Explanation
To determine the incorrect statement, let's analyze each option:
Alkali metals react with water to form their hydroxides: This statement is correct. Alkali metals react vigorously with water, giving hydrogen gas and forming their respective hydroxides.
The oxidation number of K in KO2 is +4.: This statement is incorrect. In potassium superoxide (KO2), potassium (K) actually has an oxidation state of +1. The oxygen molecule in KO2 is in the form of a superoxide ion (O2-), which has an oxidation state of -1/2 per oxygen atom. The potassium ion balances the charge, resulting in potassium's oxidation state remaining +1.
Ionisation enthalpy of alkali metals decreases from top to bottom in the group: This is correct. As we move down the group in the periodic table, the atomic size increases, and the outermost electron is farther from the nucleus, requiring less energy to remove, thus ionisation enthalpy decreases.
Lithium is the strongest reducing agent among the alkali metals: This statement is correct. Lithium has the highest tendency to lose its outer electron compared to other alkali metals, making it a very strong reducing agent. This is due to its high hydration energy.
Therefore, the incorrect statement is: The oxidation number of K in KO2 is +4.
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Concepts Used:
P-Block Elements
- P block elements are those in which the last electron enters any of the three p-orbitals of their respective shells. Since a p-subshell has three degenerate p-orbitals each of which can accommodate two electrons, therefore in all there are six groups of p-block elements.
- P block elements are shiny and usually a good conductor of electricity and heat as they have a tendency to lose an electron. You will find some amazing properties of elements in a P-block element like gallium. It’s a metal that can melt in the palm of your hand. Silicon is also one of the most important metalloids of the p-block group as it is an important component of glass.
P block elements consist of:
- Group 13 Elements: Boron family
- Group 14 Elements: Carbon family
- Group 15 Elements: Nitrogen family
- Group 16 Elements: Oxygen family
- Group 17 Elements: Fluorine family
- Group 18 Elements: Neon family