Anomalous Behaviour of Beryllium

Anomalous behaviour makes a particular element different from other members that are part of the same family. The anomalous behaviour of any element is usually due to factors such as atomic size, high electronegativity and the absence of electrons in the d-orbital. The small size means that net force on electrons increases, and hence effective nuclear force also increases. Similarly, the absence of electrons in d-orbitals means that the shielding effect of electrons does not exist; thereby, the effective nuclear force also increases. Due to these intervening effects, the chemical properties are altered, and anomalous properties are shown.

Beryllium 

Beryllium is represented as ‘Be’ on the Periodic Table of elements and has the atomic number 4. It is the first element that is present in the alkaline earth metals, and it shows an anomalous behaviour. Elements that have anomalous behaviour have different characteristics and hence help produce new compounds.

Beryllium is the first member of group-2 family metals. But when we compare it to other metals that are present in the same group, we notice that there is some anomalous behaviour that can be seen, although all the members of the group should have the same properties. It differs from the other members of the family because of some ionic and atomic properties.

In this, we have studied the first member of group 2 elements, beryllium. We get to know about the behaviour of beryllium and how it is different from other members of the group. It has this behaviour because of its small size and the absence of d-orbitals. Also, we got to know some of its similarities with aluminium as it has a diagonal relationship with beryllium.

Anomalous behaviour

Anomalous behaviour of any element is shown by some of the properties as:

• Atomic size – If the size of the atom is really small as compared to the elements of the group, then that element may show anomalous behaviour. Electrons are closely bound to a net increase in the effective nuclear force. This would mean that the element exhibits higher melting and boiling point along with a smaller atomic size.
• d-orbitals not present – The members present towards the end of the group have the presence of d-orbitals, but no d-orbitals are present in the first member of the group. Thus there is no shielding effect, and thereby the effective nuclear force increases, especially for outer shell electrons resulting in high Ionisation enthalpy.
• Electronegativity high – As the first element of any group has the highest electronegativity, it shows more different behaviour. The above effects coalesce to a higher electronegativity.

Beryllium and other metals

• Beryllium has several properties that are different from other elements of that group. These properties are:
• If we look at the melting point and boiling point of Beryllium, it is much higher than the other alkali metals of the group.
• High oxidation ionisation enthalpy leads to the formation of covalent compounds.
• The coordination number of this element is always less than four, as it has only four electrons in its valence shell.
• It has a small atomic size compared to other elements in its group.
• When we compare it with other alkali metals, it is the hardest.
• When we perform a flame test, only Beryllium does not show any colour.
• It is only metal that does not react with acids to liberate hydrogen.
• The hydroxides and oxides of Beryllium react with both acids and basic, i.e. they are amphoteric in nature.

Diagonal Similarity between Aluminium and Beryllium

Beryllium and aluminium share some properties that are anomalous behaviour of it, so they are known to have some diagonal relationship. It resembles aluminium because: 

• We know that the atomic size of beryllium is very small. It is the same as that of aluminium.
• It differs from other elements of group 2 as it forms covalent compounds, which are the same as that in aluminium.
• The hydroxide of both aluminium and beryllium are atmospheric.
• Both of these oxides have a high melting point.
• Both have the presence of oxide film on their surface.
• When we calculate the charge to radius ratio of Beryllium, it equals 0.064, and aluminium is equalled 0.060.

Uses of Beryllium

•  Non-sparking tools contain some portions of beryllium alloys.
• The conductivity of a metal is enhanced when Beryllium is added to it.
• Spacecraft, satellites and aeroplanes have contained some portions of beryllium.
• It is also used in X-ray transparency.

Conclusion  

In this, we have studied the first member of group 2 elements that are beryllium. We got to know about the behaviour of beryllium and how it is different from other members of the group. It has this behaviour because of its small size and the absence of d-orbitals. Also, we got to know some of its similarities with aluminium as it has a diagonal relationship with beryllium.