The s-Block Elements

Anomalous Behaviour of Lithium

You are aware of the use of lithium in batteries. Aren’t you? That means you are aware of what lithium is. No? Well, then let’s learn all about this element in this chapter. We will see how it behaves differently than the other group 1 elements. Let’s begin.

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Brief about Lithium

Group 1 elements in the periodic table the Alkali Metals. The first element of group 1 is lithium. So, why does it behave so differently? Well, the small size of the element is the reason for its anomalous behaviour! Let’s see how.

Nature of the Element

Lithium is extremely electropositive in nature. This is the reason why it can form covalent bonds. The polarization behaviour of its ion somewhat in the same lines as magnesium ion. Therefore, there exists a diagonal relationship between magnesium and lithium. There are a number of reasons why this diagonal relationship exists between them. Let us look at the various reasons below.

As we move from the top to bottom in a group, the electropositive nature of the elements increases. However, when we move from left to right in a period, this nature decreases. It is because of this reason that we observe similarities in the properties between diagonal elements.

We know that the size of the atoms increases from top to bottom in a group. Because of this, the polarizing power of the element decreases. However, when we move from the left to right in a period, this polarizing power keeps on increasing. This is another reason for the diagonal elements to show similar properties. Thus, we see that lithium is a strong element that is quite similar to magnesium.

Their ions have comparable boiling and melting points. Due to its small size, the atom possesses high ionization energy. It reacts with water and liquid bromine. This forms a highly stable hydride unlike most of the other alkali metals. It is interesting to note that magnesium exhibits exactly these similar properties.

Lithium

(Source: YouTube)

Similarities between Lithium and Magnesium

  • Lithium and magnesium both form monoxides.

2Mg + O2  →  2MgO

  • They both react with nitrogen to form their nitrides respectively.

Li(s) + N2(g)  →  2Li3N(s)

  • They both react slowly with water. They form oxides and hydroxides which decompose on heating.

Mg(s) + 2H2O(g)  →  Mg(OH)2(aq) + H2(g)

  • Oxides of both the elements do not form super oxides.
  • The carbonates of both decompose on heating to form the oxides and carbon-dioxide.

2 Mg(s) + CO  →  2MgO(s) + C(s)

  • Lithium chloride (LiCl) and magnesium chloride (MgCl2) are both soluble in ethanol.
  • Both the elements are less stable towards heat.

Differences between Lithium and Other Alkali Metals

  • Lithium is harder than other alkali metals.
  • Melting and boiling point is higher than other alkali metals.
  • Out of all the other alkali metals, it is the least reactive metal.
  • It is a strong reducing agent compared to other alkali metal.
  • It is the only alkali metal that forms its monoxide.
  • Compared to other alkali metals, it is not capable of forming solid hydrogen carbonates.
  • It does not react with ethyne to form ethynide. On the other hand, all other alkali metals form ethynide.
  • It reacts slowly with bromine as compared to other alkali metals.

                                                              Let us learn Alkali Metals in detail.

Solved Example for You

Q: Give some practical applications of lithium.

Ans:

  • We use it in the manufacturing of batteries.
  • It is used in the glass and ceramic industry.
  • It finds its use in the polymers and drug industries as well.
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