Classify elements in the periodic table according to spdf blocks
Answers
Answer:
The position of an element in the periodic table is based on its valence shell electronic configuration.
Based on the type of atomic orbitals which receives the last electron or differentiating electron the elements are categorized as s-, p-, d- and f-block elements.
There are two exceptions to this classification. The first exception is Helium. Based on its electronic configuration, it should be placed in the s-block in the periodic table.
But it is placed in the p-block with the other Group 18 elements.
This is because, like other Group 18 elements, helium has a completely filled valence shell and as a result exhibits characteristic properties of other noble gases.
The other exception is Hydrogen which has only one electron in the s-orbital; and therefore can be placed in Group 1 with other alkali metals.
However, hydrogen can also gain an electron to achieve the nearest noble gas configuration of Helium. And hence can be placed along with halogens in group 17.
Therefore, it is considered as a special case and is placed separately on the top of the periodic table.
The s-block of the periodic table consists of elements that have the last electrons entered the ns orbital.
The alkali metals in Group 1 and the alkaline earth metals in Group 2 of the long form of the periodic table belong to this category.
These are soft metals with low melting and boiling points with a valence shell electronic configuration of ns¹ and ns² respectively, these elements have extremely low ionization enthalpies, they easily lose their outermost electrons to form uni-positive, ions in the case of alkali metals or dipositive ions in the case of alkaline earth metals. Therefore, the compounds formed by the s-block elements with the exception of those formed by lithium and beryllium are ionic in nature.
Due to low ionization enthalpies, s-block elements are highly reactive and therefore, are never found in pure form in nature. They always occur in the combined form in nature.
Ex: Magnesium occurs in the combined state as carbonates, sulphates, chlorides and silicates but never as pure magnesium.
Minerals of Magnesium
Carbonate
Magnesite
MgCO₃
Dolomite
MgCO₃. CaCO₃
Sulphate
Epsam salt
MgSO₄.7H₂O
Kieserite
MgSO₄. H₂O
Chloride
Carnalite
MgCl₂. KCl. 6H₂O
Silicate
Asbestos
Mg₃(Si₄O₁₀)(OH)₄
Talc
Mg₃(Si₄O₁₀)(OH)₂
The metallic character and chemical reactivity of s-block elements increase as we go down the group.
The elements of Group 13 to 18, situated at the right side in the long form of periodic table belong to p- block.
The p-block elements together with the s-block elements are called the representative elements or main group elements.
The p-block elements have their last electron entering the p orbital; this result in an outermost electronic configuration varying from ns² np¹ to ns² np⁶. At the end of each period is a noble gas element with a stable configuration of ns² np⁶.
The p- block consists of metals, non-metals and metalloids.
The nonmetallic character increases across a period and the metallic character increases as we go down the group.
The p-block elements form compounds by loss or gain of electrons, or by sharing the valence electrons. So they can form both ionic as well as covalent bonds.
Two chemically important groups of p-block elements are Group-16 (chalcogens) and Group -17 (halogens).
The elements of these two groups have high negative gain enthalpies and they readily gain one or two electrons to attain the stable noble gas electronic configuration which is ns2 np6.