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The s-block is one of four blocks of elements on the periodic table. The s-block group have a common property. The electron in their most outward electron shell are in the s-orbital. Elements in the s-block are in the first two periodic table groups. The elements in group one are called the alkali metals. The elements in group two are called the alkaline earth metals.
The modern periodic law says that "The properties of elements are periodic function of their atomic number." This means that some properties of elements are repeated as the atomic number of the elements gets larger. These repeating properties have been used to separate the elements into four blocks. These blocks are s-block, p-block, d-block, and f-block.
Diagonal relationship[change | change source]
The first element in group one, Lithium, and the first in group two, Beryllium, behave differently to other members of their groups. Their behaviour is like the second element of the next group. So lithium is similar to magnesium, and beryllium is similar to aluminum.[source?]
In the periodic table this is known as a Diagonal relationship. The diagonal relationship is because of similarities in ionic sizes and charge/radius ratio of the element. The similarity between lithium and magnesium is because of their similar sizes:[source?]
- Radii, Li=152pm Mg=160pm
Lithium[change | change source]
Lithium has many different behaviours to other elements in group one. This difference caused by:
- the small size of the lithium atom and its ion.
- the higher polarization power of li
+ (i.e. charge size ratio). This means increased covalent character of its compounds which is responsible for their solubility in organic solvents
- high ionisation enthalpy and low electropositive character of lithium as compared to other alkali metals
- non availability of d-orbitals in its valence shell
- strong intermetallic bonding
Some of the ways in which lithium behaves differently from other members of are:[source?]
- Lithium is harder than sodium and potassium which are so soft that they can be cut by a knife.
- The melting and boiling points of lithium are higher.
- Lithium forms monoxide with oxygen, other alkali form peroxide and superoxide.
- Lithium combines with nitrogen to form nitrides, while other alkali metals do not.
- Lithium Chloride is deliquescent and crystallizes as a hydrate LiCl.2H2O. Other alkali metal chlorides do not form hydrates.