In the atoms of the p-block elements, the last electron enters the p-subshell of the outermost shell. In these elements np subshell is gradually filled up. The valency shell configuration varies from ns2 np1 to ns2 np6.
These elements include some metals, all non-metals and metalloids. s-block and p-block elements are collectively called normal or representative elements (except zero group elements). Each period ends with a member of zero group (18th group), i.e., a noble gas with a closed shell ns2np6configuration. Prior to noble gas group, there are two chemically important groups of non-metals. These are halogens (group 17) and chalcogens (group 16).
General Characteristics of p-Block Elements:
1. p-block elements consist of the elements of six groups, viz. IIIA, IVA, VA, VIA, VIlA and zero group. The number of electrons in the outermost shell varies from .3 to 8, i.e., they have a general configuration, ns2np1-6. The number of electrons in the penultimate shell is either 2 or 8 or 18.
2. 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.
3. The p-block elements generally show covalency but higher members can show electrovalency. The highly electronegative elements like halogens, 0, 5, N, etc., show electrovalency by accepting electrons and forming anions. Some of the elements show coordinate valency also.
4. 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.
5. Ionisation energies increase from left to right in a period while decrease in a group from top to bottom. The members of V group and zero group have exceptionally high values of ionisation energies on account of half-filled and fully filled orbitals in the valency shell.
6. In every period, reducing nature decreases from left to right while oxidising nature increases. Reducing nature increases in a group from top to bottom. Halogens are strong oxidising agents.
7. Most of them are highly electronegative. The electronegativity increases in a period from left to right and decreases in a group from top to bottom.
8. Most of them form acidic oxides.
9. No member of p-block series or the salts imparts a characteristic colour to the flame.
10. Chemical properties change from group to group. It is difficult to summarise them.
11. A number of elements of p-block series show the phenomenon of allotropy. Carbon, silicon, phosphorus, sulphur, boron, germanium, tin, arsenic, etc., show this property.
12. Catenation property is shown by many elements of p-block series such as carbon, silicon, germanium, nitrogen, oxygen, sulphur, etc.
General characteristics of group IIIA or 13 elements
Group IIIA or 13 of the periodic table consists of six elements-boron, aluminium, gallium, indium, thallium and ununtrium. These are p-block elements as the last differentiating electron enters np orbital. The configuration of the outermost energy shell is ns2 np1, i.e., this group marks the beginning of the p-block elements. Since the members of this group possess three electrons in the outermost or in their valency shell, they have many similarities in their properties. However, the penultimate shell (next to the outermost) contains i-grouping in boron, s2p6 (8 electrons) in aluminium and s2p6d10 (18 electrons) in other elements (Ga, In, Tl and Uut). This shows why boron differs from aluminium and both boron and aluminium having noble gas kernel differ from other four elements.
General characteristics of group IVA or 14elements
Group IVA or 14 of periodic table consists of six elements carbon (C), -silicon (Si), gennanium (Ge), tin (Sn), lead (Pb) and ununquadium. These six elements constitute a family known as carbon family. These are p-block elements as the last differentiating electron is accommodated in the np shell. These elements have four electrons in their valency shell and thus are placed in the IVthgroup.
The configurations show that these elements have the same number of electrons in the valency shell, i.e., 4 electrons in the valency shell, two of which are in s-orbital while remaining two in p-orbitals. Thus, they have ns2 np2 configuration, i.e., s-orbital is paired while two p-orbitals are unpaired.
The penultimate shell of carbon contains 2 electrons (saturated), of silicon contains 8 electrons (saturated), and of germanium contains 18 electrons (saturated) while Sn and Pb contain 18 electrons (unsaturated) each. This shows why carbon differs from silicon in some respects and these two differ from rest of the members of this group. The close resemblance between the elements is quite striking in the case of elements of the first and second groups, but this becomes less evident in the elements of third group and still less evident in the fourth group
General characteristics of group VA or 15 elements
VA group or 15th group of the extended form of the periodic table consists of six elements-nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi) and ununpentium (Uup)*. This group of six elements constitutes a family. These elements are collectively known as pnictogens. These are p-block elements as the last differentiating electron is accommodated in the np shell. These elements have five electrons in the valency shell. The elements of the group possess the same electronic configuration and show similarities as well as gradation in their properties with rise of atomic number from nitrogen to ununpentium.
The configurations show that these elements have the same number of electrons in the valency shell, i.e., 5 electrons in the valency shell, two of which are in the s-orbital and remaining three in three p-orbitals. Thus, they have ns2 np3 configuration, i.e., s-orbital is paired and three p orbitals are unpaired.
The penultimate shell in nitrogen contains 2 electrons (saturated), in phosphorus contains 8 electrons (saturated), in arsenic contains 18 electrons (saturated) while in antimony and bismuth contain 18 electrons (unsaturated) each. This shows why nitrogen differs from phosphorus in some respects and these two differ from the remaining elements of this group.
In accordance with the Hund's rule, electronic configurations involving fully filled or exactly half filled orbitals are the most stable, the elements of group VA, having exactly half filled orbitals, are also fairly stable and not so reactive. Nitrogen behaves as a noble element under ordinary conditions.
General characteristics of group VIA or 16 elements
Group 16 or VIA of the extended form of periodic table consists of six elements oxygen (O), sulphur (S), selenium (Se), tellurium (Te), polonium (Po) and ununhexium (Uuh). This family is known as oxygen family. These (except polonium and ununhexium) are the ore forming elements and thus called chalcogens. These are p-block elements as the last differentiating electron is accommodated on np shell. These elements have six electrons in their valency shell and thus placed in the VIth group. The elements oxygen and sulphur are common while selenium, tellurium and polonium are comparatively rare. Oxygen is the most abundant element and is found both in free as well as in combined state. Oxygen makes up 20.9% by volume and 23% by mass of atmosphere. Most of the oxygen present in the atmosphere is produced by photosynthesis in plants. It also occurs in the form of ozone in the upper atmosphere which protects us from the harmful radiations of the sun. Oxygen makes up 46.6% by mass of the earth's crust. Sulphur is the sixteenth most abundant element and constitutes 0.034% by mass of the earth's crust. It occurs mainly in the combined form. The member, polonium is radioactive in nature. The inclusion of these elements in the same subgroup is justified on the basis of same electronic configuration and similarities as well as gradation in their physical and chemical properties.
General characteristics of group VIIA or 17 elements
17th or VIIA group of the periodic table (extended form) consists of five elements; fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At). This group of five elements forms a family known as the halogen family as their salts are found in sea water. Halogen is a Greek word meaning a sea salt. Halogens are p-block elements as the last differentiating electron is accommodated on np subshell. These elements have seven electrons in their valency shell and are thus placed in VII group of the periodic table.
Except for astatine, the members are found in combined state in considerable quantities in nature. Astatine is unstable element of radioactive origin. Astatine is radioactive artificially prepared element. These elements possess the same electronic configuration and show similarities as well as gradual gradation in their physical and chemical properties.
General characteristics of group VIIIA or 18 elements
The zero or 18th group consists of seven dements; helium, neon, argon, krypton, xenon, radon and ununoctium. The zero group was unknown when Mendeleev presented the periodic table and has been inserted in the table only at a later stage. The existence of such a group may be naturally expected from the factthat there must be art inert group as transition when we go from highlyelectronegative elements (halogens) to highly electropositive elements (alkali metals). Thus, zero group occupies the intermediate position between the elements of VIIA (17th) and IA (lst) groups.