· Thevertical columns in the periodic table are called groups or families. · Thereare nine groups in all including viii group consisting of three triads and zerogroup of inert gases. · GroupsI to VII are sub-divided into sub-group A & B. · Elementsof group IA to group A have their outermost shells incomplete while each oftheir inner shell is complete. These elements are called normal orrepresentative elements. These elements consist of some metals, all non-metalsand metalloids. · Elementsof groups IB, IIB, IIIB (only Sc, Y, La & Ac), IVB, VB, VIB, VIIB &VIII have their two outermost shell incomplete. These are called transitionelements. All these are metals. · Elementsof zero group have all their shells completely filled. These are noble gases. · Twogroups of 14 elements lying in group IIIB [Ce(z = 58) and Th(z = 90) to Lw(z =103)] have their three outmost shells incomplete. There are known aslanthanides and actinides respectively. · Thehorizontal rows in the periodic table are called periods. · Thereare seven periods in the periodic table. · Firstperiod consist of two elements H & He. · Secondand third period are 8 elements each. Second period → from Li to Ne &3rd period→ from Na to Ar both these are short period. · Fourthand fifth periods have 18 elements each. 4th period → from K toKr & 5th period → from Rb to Xe. These are long periods. · Sixthperiod has 32 elements from Ca to Rn. It is the longest period. It alsoincludes 14 lanthanides. · Sevenperiod is incomplete. This period also includes 14 actinides. The elementsafter U(z = 92) are called transuranic elements. These elements are the resultof atomic research and hence are synthetic elements. · Allthe elements of a given group possess very similar chemical and physicalproperties. These are regular gradation in their properties when we move fromtop to bottom in a group. · Sizeof atoms increases on descending a group. · Themetallic character of the elements increases in moving from top to bottom in agroup. · Ingoing down a group, the number of electron shells increases by one at each stepand ultimately becomes equal to the number of the period to which the elementbelongs. · Numberof valency electrons increases 1 to 8 as we proceed from left to right in aperiod. · Sizeof atoms decreases from left to right in a period. · Fromleft to right in a period, metallic character of the element decreases. · Diagonalrelationship is the resemblance of the properties of the elements of 2ndperiod with their diagonal opposite members lying in 3rd period. · Examplesof diagonal relationship found in the periodic table are Li-Mg; Be-Al;B-Si. · Inthe atoms of these electrons, the last electron enter the S-orbit of theultimate shell. · Valenceshell electronic configuration varies from ns1 to ns2. · Elementsof group IA, group IIA and He belongs to this block. · Inthe atoms of these elements, the last electron enters the p orbit of theultimate shell. · Valenceshell configuration varies from ns2 np1 to ns2np6. · Elementsof the group IIIA, IVA, VA, VIA, VIIA & zero group (Ne to Rn) belongs tothis block. · Inthe elements, either in their atomic states or in any of their common oxidationstates, the last electron enter the d-orbit of the penultimate shell i.e. thelast electron goes to the (n-1) d-orbit. · Withthe exceptions of Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, Pt & Au, in the atoms ofthese elements the ns orbital is completely filled. Consequently, the valenceshell configuration of these elements varies from (n-1)d1 ns2 (groupIIIB) to (n-1) d10 ns2 (group IIB) configuration. · Theelements of group IIIB, IVB, VB, VIB, VIII, IB & IIB belong to this block. · Theseelements are classified into four series i.e. 3d, 4d, 5d & 6d orbitals of 3rd,4th, 5th & 6th shell respectively. · Inthese elements, either in the atomic state or in any of their common oxidationstates, the last electron enters the f-orbit of ante-penultimate shell. · Thevalence shell electron configuration of theatoms of these elements is represented as: (n-2)ƒ1-7,9-14,(n-1)d0,1.ns2. · Theseelements are located in group IIIB and have been given a separate place at thebottom of the periodic table. · Theseare classified into two series i.e 4ƒ and 5ƒ corresponding to the filling of 4ƒand 5ƒ orbitals of 4th and 5th shells respectively.
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