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# Peculiar Properties Of Beryllium And Lithium

S-block elements of the modern periodic table such as lithium and beryllium exhibit unique properties with respect to other elements in the same group due to various reasons.

Lithium: Lithium exhibits distinct properties due to the small size of the lithium atom, high polarising power (ratio of charge to the radius) and hydration energy. This increases the covalent nature of lithium compounds.

Anomalous behaviour of lithium with respect to other alkali metals:

• The melting point and boiling point of lithium are higher than other alkali metals.
• The hardness of lithium is higher than other metals.
• The alkali metal chlorides do not have the capability to form hydrates but lithium chloride crystallises to form a hydrate

$$\begin{array}{l}LiCl_2.H_2O\end{array}$$

• Lithium nitrate decomposes to form an oxide whereas other metals on heating give nitrites.
• Compounds of lithium are partially soluble in water whereas the alkali metals are highly soluble in water.

Beryllium: The anomalous properties of beryllium are mainly due to its small size, high electronegativity, high ionization energy and high polarizing power compared to the other elements in the group. The anomalous properties of beryllium compared to other elements of the group are as mentioned below:

• The coordinate number of beryllium is not more than 4 whereas other alkali metals have a coordinate number of 6.
• The melting point and boiling points are higher when compared to the other elements of the group.
• They form covalent bonds whereas the other members of the group form ionic bonds.
• Be does not react with water like the other companions of the group.

## Frequently Asked Questions – FAQs

### What is common between beryllium and lithium?

Both lithium and beryllium are present in the same second period.

### Are beryllium and lithium covalent in nature?

Lithium and beryllium have high polarising powers due to which they distort the electron cloud of the anion and hence according to Fajans rule form covalent bonds.

### Why is lithium so important?

It is the metal with the lowest density. It has a strong reaction with water. The most common application for lithium is in rechargeable batteries for cell phones, laptop computers, digital cameras, and electric vehicles.

### The first member of the s-block elements differs from the rest of their members considerably. Why?

Lithium and Beryllium, the first members of the s-block family differ much from the rest of their members. The anomaly of these elements is due to their,
a. Low atomic and ionic size
b. Greater charge density (charge/volume of the atom)
c. Greater polarization and
d. Absence of ’d’ orbitals.

Download the BYJU’S learning app from android play store or app store to understand the anomalous properties of the first element of each group in the S-Block of the periodic table.’

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