Anomalous Behaviour of Beryllium: Chemistry Class 11

Anomalous Behaviour of Beryllium: Have you ever seen or met anyone who has six fingers or conjoined twins? If you answered yes, you might have noticed that they differ from the normal form of the body. Anomalies exist both in people and things, elements in the periodic table exhibit anomalies as well.

In simple terms, anomaly can be explained as the difference in behaviour when compared to other elements in a particular group. In this article, we will study the element of group \(2\) that shows the anomalous behaviour of Beryllium.

Anomalous Behaviour: Details

Anomalous behaviour is a behaviour that differs from the normal or original order. It differs from the other members of its group in terms of properties. Anomalous elements have distinct characteristics and produce different compounds.

The anomalous behaviour in elements of the periodic table is shown due to the following three factors-

1. Small size- Atoms and ions are much smaller in size than other elements in the group.
2. High electronegativity- The first element has the highest electronegativity.
3. Non-availability of d–orbitals- The higher members of the group belonging to higher periods possess d–orbitals and may utilize them for bond formation.

Beryllium is a chemical element with atomic number \(4\) and the symbol ‘Be’. It is the first member of alkaline earth metal and shows anomalous behaviour. It’s a steel-grey metal that’s strong, light, and brittle. It is a divalent element that only occurs in nature in the form of minerals when combined with other elements.

Anomalous Behaviour of Beryllium

Beryllium, the first member of group \(2,\) differs from the other elements of its own group in several properties and thus shows an anomalous behaviour. The anomalous behaviour of Beryllium is due to the following factors:

1. It is the smallest of all other alkaline earth metal atoms.
2. It has the highest ionization energy.
3. The electronegativity of Beryllium is comparatively higher than other elements.
4. It does not possess vacant d-orbitals in its valence shell.

Due to higher electronegativity, the compounds of Beryllium are predominantly covalent. This is because when Beryllium combines with some other element, the difference in the electronegativity of the two is usually low.

Difference Between Beryllium and other Alkaline Metals

Some important properties in which Beryllium differs from other alkaline metals are as follows:

1. Beryllium is the hardest of all other alkaline earth metals.
2. It has higher melting and boiling points as compared to other elements.
3. Beryllium does not impart colour during the flame test.
4. Beryllium compounds are predominantly covalent, while those of other elements are predominantly ionic.
5. It does not decompose water even at high temperatures, while the other elements of the group do so.
6. It does not react with acids to liberate hydrogen, while the other elements of the group do so.
7. Its oxide, \(\mathrm{BeO}\) is amphoteric, while the oxides of the other elements are basic in nature.
   \({\rm{BeO}} + 2{\rm{HCl}} \to {\rm{BeC}}{{\rm{l}}_2} + {{\rm{H}}_2}{\rm{O}}\)
   \(\mathrm{BeO}+2 \mathrm{NaOH} \rightarrow \mathrm{Na}_{2} \mathrm{BeO}_{2}+\mathrm{H}_{2} \mathrm{O}\)
8. Beryllium shows a maximum coordination number of \(4\) in its complex compounds, while the other elements of the group can have a coordination number of \(6\) in their complex compounds. This is due to the unavailability of vacant d-orbitals in the valence shell of Beryllium. Other elements of the group possess vacant d-orbitals and can utilize them in acquiring a coordination number of \(6.\)

Difference Between Beryllium and Magnesium

Some important properties in which Beryllium differs from magnesium are as follows:

1. Beryllium is lighter than magnesium.
2. Beryllium does not react with water, while magnesium reacts with boiling water.
3. \({\rm{BeO}}\) is amphoteric, while \(\mathrm{MgO}\) is weakly basic.

Resemblance of Beryllium with Aluminium (Diagonal Relationship)

The following points illustrate the anomalous behaviour of \({\rm{Be}}\) and its resemblance with \({\rm{AI}}\)

1. The charge/radius ratio of Beryllium and aluminium ions is nearly the same.
2. Beryllium, unlike the other group \(2\) elements, but like aluminium, produces covalent compounds.
3. The hydroxides of \({\rm{Be,}}\left[ {{\rm{Be(OH}}{{\rm{)}}_{\rm{2}}}} \right],\) and aluminium, \(\left[\mathrm{Al}(\mathrm{OH})_{3}\right],\) are amphoteric, whereas those of other group \(– 2\) elements are basic.
4. Both \({\rm{Be}}\) and \({\rm{AI}}\) oxides, i.e., \({\rm{BeO}}\) and \({\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\) are high melting insoluble solid.
5. \(\mathrm{BeCl}_{2}\) and \(\mathrm{AlCl}_{3}\) have bridged chloride polymeric structures. Both the chlorides are soluble in organic solvents like benzene, chloroform, etc., and behave as strong Lewis acid. They are also used as a catalyst in Friedel-craft’s reaction.

6. Both beryllium and aluminium salts are extensively hydrolyzed.
7. Both metal carbides react with water to produce methane gas.
\({\rm{B}}{{\rm{e}}_2}{\rm{C}} + 4{{\rm{H}}_2}{\rm{O}} \to 2{\rm{Be}}{({\rm{OH}})_2} + {\rm{C}}{{\rm{H}}_4}\)
\(\mathrm{Al}_{4} \mathrm{C}_{3}+12 \mathrm{H}_{2} \mathrm{O} \rightarrow 4 \mathrm{Al}(\mathrm{OH})_{3}+3 \mathrm{CH}_{4}\)
8. Both \({\rm{Be}}\) and \({\rm{AI}}\) have amphoteric oxides and hydroxides that dissolve in sodium hydroxide and hydrochloric acid.
\(\mathrm{BeO}+2 \mathrm{NaOH} \rightarrow \mathrm{Na}_{2} \mathrm{BeO}_{2}+\mathrm{H}_{2} \mathrm{O}\)
\(\mathrm{Al}_{2} \mathrm{O}_{3}+6 \mathrm{HCl} \rightarrow 2 \mathrm{AlCl}_{3}+3 \mathrm{H}_{2} \mathrm{O}\)
9. Like aluminium, Beryllium is resistant to acid degradation because of the presence of an oxide film.

Beryllium: Uses

1. Gyroscopes, springs, electrical contacts, spot-welding electrodes, and non-sparking tools are made with beryllium alloys containing copper or nickel.
2. Any metal can be made more electrically and thermally conductive by combining Beryllium with it.
3. High-speed aeroplanes, weapons, spacecraft, and communication satellites all utilize beryllium alloys as structural materials.
4. Beryllium is also used in X-ray lithography since it is X-ray transparent.

Summary

In this article, we studied that the first element of the respective groups shows different properties than the rest of the elements due to their smaller size, high electronegativity and Absence of vacant d-orbitals. Now we know the points of differences between alkaline earth metals and Beryllium, also, the similarity of Beryllium with that of aluminium due to diagonal relationship.

Study Structure of Atom From Here

FAQs on Anomalous Behaviour of Beryllium

Q.1. What is anomalous behaviour?
Ans: An anomalous behaviour is a behaviour that differs from the normal or original order. It differs from the other members of its group in terms of properties. Anomalous elements have distinct characteristics and produce different compounds.
The anomalous behaviour in elements of the periodic table is shown due to the following three factors such as Small Size, High electronegativity and non-availability of d-orbitals.

Q.2. What is the reason for BE’s (Beryllium’s) anomalous behaviour?
Ans: The anomalous behaviour of Beryllium is due to the following factors:
i. It is the smallest of all other alkaline earth metal atoms.
ii. It has the highest ionization energy.
iii. The electronegativity of Beryllium is comparatively higher than other elements.
iv. It does not possess vacant d-orbitals in its valence shell.

Q.3. Why is Beryllium not considered in earth metals?
Ans: Because of two factors, alkaline metals are referred to as such.
i. They are mined in the form of ores from the earth.
ii. Their oxides and hydroxides have alkaline (basic) properties.
Beryllium fulfils the first but not the second condition because its oxides and hydroxides are amphoteric rather than alkaline. As a result, it isn’t classified as an alkaline earth metal.

Q.4. The similarity between aluminium and Beryllium is due to which reason?
Ans: The similarity between aluminium and Beryllium is due to the diagonal relationship.

Q.5. State the difference in properties between Beryllium and magnesium.
Ans: Some important properties in which Beryllium differs from magnesium are as follows:
i. Beryllium is lighter than magnesium.
ii. Beryllium does not react with water, while magnesium reacts with boiling water.
iii. \({\rm{BeO}}\) is amphoteric, while \(\mathrm{MgO}\) is weakly basic.