Choose the correct order of density of the alkali metals :
- \(Li < K < Na < Rb < Cs\)
- \(Li < Na < K < Rb < Cs\)
- \(Cs < Rb < K < Na < Li\)
- \(Li < Na < K < Cs < Rb\)
The Correct Option is A
Solution and Explanation
Hence, the correct option A: \(Li < K < Na < Rb < Cs\)
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Concepts Used:
Group 1 Elements
Group one of alkali metals is s-block elements with just one electron in their s-orbital. They are are alkali metals. They are named so because of the alkaline nature of the hydroxides and oxides.
Alkali metals are characterized by one s-electron in the valence shell of their atoms.
Alkali metals have a corresponding [Noble gas] ns1 electronic configuration. They occupy the first column of the periodic table. Alkali elements are:
- Lithium(Li)
- Sodium(Na)
- Potassium (K)
- Rubidium (Ru)
- Cesium (Cs)
- Francium (Fr)
They have occupied successive periods from first to seven. Francium is a radioactive element with very low half-life.
Electronic Configuration:
- Alkali metals have one electron in their valence shell.
- The electronic configuration is given by ns1. For example, the electronic configuration of lithium is given by 1ns1 2ns1.
- They tend to lose the outer shell electron to form cations with charge +1 (monovalent ions).
This makes them the most electropositive elements and due to the same reason, they are not found in the pure state.