Inorganic chemistry

What are p-Block Elements?

Those elements in which the last electron occupies p-orbitals and are placed together in groups 13, 14, 15, 16, and 17 (Except Helium) are called p-block elements. As p-block orbitals can accommodate totals of a maximum of six electrons that’s why p-block elements have been divided into six groups.

Each group of p-block elements is recognized by its first element. Group 13 is called Boron Family, group 14 is called Carbon Family, group 15 is called Nitrogen Family, Group 16 is called Oxygen Family, group 17 is called Halogen or fluorine Family, group 18 is called Noble Gas Family or Neon Family. Here you need to keep in mind that Helium is not a p-block element although it is a part of the noble gas family as it's also a noble gas. Helium is a part of s-block elements.

These elements include some metals, all nonmetals, and metalloids. s-block and p-block elements are collectively called normal or representative elements (except zero group elements). Each period of the periodic table ends with a member of zero groups (18th group), i.e., a noble gas with a closed shell ns2np6 configuration. Prior to the noble gas group, there are two chemically important groups of non-metals. These are halogens (group 17) and chalcogens (group 16).

In this article, you will get to know about the properties of p-block elements and their uses.

Properties or Characteristics of p-Block Elements

🔹In the atoms of the p-block elements, the last electron enters the p-subshell of the outermost shell.

🔹In these elements, the np subshell is gradually filled up. The valence shell configuration varies from ns2 np1 to ns2 np6.

🔹The general electronic configuration of elements of p-block is ns2np1-6 (Except Helium).

🔹 The number of electrons in the penultimate shell of p-block elements is either 2 or 8 or 18.

🔹Except for F and inert gases, p-block elements show a number of oxidation states from +n to (n- 8) where n is the number of electrons present in the outermost shell.

🔹The p-block elements generally show covalency but higher members can show electrovalency. The highly electronegative elements like halogens F, Cl etc., show electrovalency by accepting electrons and forming anions. Some of the elements show coordinate valency also.

🔹In the period from left to right, there is a regular increase in non-metallic character. However, non-metallic character decreases in the groups from top to bottom

🔹Ionization energies increase from left to right in a period while decreasing in a group from top to bottom. The members of group VA and zero group have exceptionally high values of ionization energies on account of half-filled and fully filled orbitals in the valence shell.

🔹In every period, reducing nature decreases from left to right while oxidizing nature increases. Reducing nature increases in a group from top to bottom. Halogens are strong oxidizing agents.

🔹Most of the p-block elements form acidic oxides.

🔹No member of the p-block series or the salts imparts a characteristic color to the flame.

🔹A number of elements of the p-block series show the phenomenon of allotropy. Carbon, silicon, phosphorus, sulfur, boron, germanium, tin, arsenic, etc., show this property.

🔹Most of the p-block elements form acidic oxides. No member of the p-block series or the salts imparts a characteristic color to the flame.A number of elements of the p-block series show the phenomenon of allotropy. Carbon, silicon, phosphorus, sulfur, boron, germanium, tin, arsenic, etc., show this property.

Uses of p-Block Elements

p-block elements are used in various fields in so many ways. We have listed here a few uses of p-block elements –

🔹 A compound of boron called borax is used in the glass making industry and pottery.

🔹Boron is also used in the soap or detergent industry.

🔹Boron is used in aircrafts and bullet proof vests.

🔹Boron is used in steel to increase its hardness.

🔹Aluminum is used in utensils, coils, cables, protection of iron and zinc, foils to wrap articles. It is used as a reducing agent as well.

🔹Germanium, arsenic, silicon, gallium are used as semiconductors.

🔹 Fitkari is used for the purification ofthe water and antiseptic.

🔹Iodine is used in iodine tincture.

🔹Chlorine is used in disinfectants.

🔹Carbon and its compounds are used in numerous ways.

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Table of Content -

1-Coordination Complex
2-Types

Double Salts and Coordination Complex
Double Salts

Double salts are completely ionizable in aqueous solutions and each ion in the solution gives the corresponding confirmatory test.

Example: Potash Alum is double sulphate. It is K2SO4.Al2(SO4)3.24H2O on Ionization it gives:

K+, SO2−4 and Al+3 ions which response to the corresponding tests.

Coordination Complex -

Co-ordinate complex are incompletely ionizable in the aqueous solutions. These give a complexion which does not show complete ionization.

Example: Potassium Ferrocyanide. [K4Fe(CN)6] It ionizes to give K+ and [Fe(CN)6]−4 [ferro cyanide ions]

Types of Coordination Complexes
1-Cationic complexes: In this co-ordination sphere is a cation. Example: [Co(NH3)6]Cl3
2-Anionic complexes: In this co-ordination sphere is Anion. Example: K4[Fe(CH)6]
3-Neutral Complexes: In this co-ordination sphere is neither cation or anion. Example: [Ni(CO)4]
4-Homoleptic complex: The complex consist of a similar type of ligands. Example: K4[Fe(CN)6]
5-Heteroleptic complexes: These consists of different types of ligands. Example: [Co(NH3)5Cl]SO4
6-Mononuclear complexes: In this co-ordination sphere has single transition metal ion. Example: K4[Fe(CN)6]
7-Polynuclear complexes: More than one transition metal ion is present. Example:

What are Coordination Compounds?
Coordination compounds are chemical compounds that consist of an array of anions or neutral molecules that are bound to a central atom via coordinate covalent bonds. Coordination compounds are also referred to as coordination complexes. These molecules or ions that are bound to the central atom are referred to as ligands (also known as complexing agents).
Table of Content
1-Important Terms
2-Properties of Coordination Compounds

Many coordination compounds contain a metallic element as the central atom and are therefore referred to as metal complexes. These types of coordination complex generally consist of a transition element as the central atom. It can be noted that the central atom in these complexes is called the coordination centre.

Important Terms Involving Coordination Compounds
The definitions of some important terms in the chemistry of coordination compounds can be found below.

Coordination Entity
A chemical compound in which the central ion or atom (or the coordination centre) is bound to a set number of atoms, molecules, or ions is called a coordination entity.

Some examples of such coordination entities include [CoCl3(NH3)3], and [Fe(CN)6]4-.
Central Atoms and Central Ions
As discussed earlier, the atoms and ions to which a set number of atoms, molecules, or ions are bound are referred to as the central atoms and the central ions.

In coordination compounds, the central atoms or ions are typically Lewis Acids and can, therefore, act as electron-pair acceptors.

Ligands
The atoms, molecules, or ions that are bound to the coordination centre or the central atom/ion are referred to as ligands.

These ligands can either be a simple ion or molecule (such as Cl– or NH3) or in the form of relatively large molecules, such as ethane-1,2-diamine (NH2-CH2-CH2-NH2).

Coordination Number
The coordination number of the central atom in the coordination compound refers to the total number of sigma bonds through which the ligands are bound to the coordination centre.

For example, in the coordination complex given by [Ni(NH3)4]2+, the coordination number of nickel is 4.

Coordination Sphere
The non-ionizable part of a complex compound which consists of central transition metal ion surrounded by neighbouring atoms or groups enclosed in square bracket.

The coordination centre, the ligands attached to the coordination centre, and the net charge of the chemical compound as a whole, form the coordination sphere when written together.

This coordination sphere is usually accompanied by a counter ion (the ionizable groups that attach to charged coordination complexes).

Example: [Co(NH3)6]C/3 – coordination sphere
Coordination Polyhedron
The geometric shape formed by the attachment of the ligands to the coordination centre is called the coordination polyhedron.

Examples of such spatial arrangements in coordination compounds include tetrahedral and square planar.

Oxidation Number
The oxidation number of the central atom can be calculated by finding the charge associated with it when all the electron pairs that are donated by the ligands are removed from it.

For example, the oxidation number of the platinum atom in the complex [PtCl6]2- is +4.

Homoleptic and Heteroleptic Complex

1-When the coordination centre is bound to only one type of electron pair donating ligand group, the coordination complex is called a homoleptic complex, for example: [Cu(CN)4]3-.
2-When the central atom is bound to many different types of ligands, the coordination compound in question is called a heteroleptic complex, an example for which is [Co(NH3)4Cl2]+.

Properties of Coordination Compounds

The general properties of coordination compounds are discussed in this subsection.

1-The coordination compounds formed by the transition elements are coloured due to the presence of unpaired electrons that absorb light in their electronic transitions. For example, the complexes containing Iron(II) can exhibit green and pale green colours, but the coordination compounds containing iron(III) have a brown or yellowish-brown colour.
2-When the coordination centre is a metal, the corresponding coordination complexes have a magnetic nature due to the presence of unpaired electrons.
3-Coordination compounds exhibit a variety of chemical reactivity. They can be a part of inner-sphere electron transfer reactions as well as outer-sphere electron transfers.
4-Complex compounds with certain ligands have the ability to aid in the transformation of molecules in a catalytic or a stoichiometric manner.