4 th Transition series includes the elements in which the sublevel 6d is filled successively, It consists of 10 elements and it is placed in the 7 th period.3 rd Transition series includes the elements in which the sublevel 5d is filled successively, It consists of 10 elements, It is placed in the 6 th period, It starts by lanthanum 57La (5d¹) and ends with mercury 80Hg (5d 10).2 nd Transition series includes the elements in which the sublevel 4d is filled successively, It consists of 10 elements, It is placed in the 5 th period, It starts by yttrium 39Y (4d¹) and ends with cadmium 48Cd (4d 10).1 st Transition series includes the elements in which the sublevel 3d is filled successively, It consists of 10 elements, It is placed in the 4 th period, It starts by scandium 21Sc (3d¹) and ends with zinc 30Zn (3d 10).d-block Elementsĭ-block Elements : ( Main Transition elements) are elements in which the sublevel d is successively filled with increasing atomic number, They lie in 10 vertical columns since the d-sublevel consists of 5-orbitals filled with 10 electrons, Ten vertical columns are represented by 8 groups (seven of which belong to group B) and the other three belong to group VIII, They are divided into 4 series which are: P-block Elements (nS 2, nP 1→6 ) are placed in right-hand block of the table, the outermost electrons occupy the p-sublevel, They are six groups (III-A, IV-A, V-A, VI-A, VII-A, and group number zero of noble gases, Since the P-sublevel consists of 3 orbitals which are filled with 6 electrons. S-block elements (nS 1→2) are placed in the left-hand block of the table, the outer most electrons occupy the S-sublevel, It consists of two groups of elements, I-A and II-A, since the S-sublevel consists of one orbital filled with 2 electrons, The electronic configuration of group I-A is nS¹ and group II-A is nS², where n is the number of outer energy level and the number of period at the same time. The electronic configuration becomes more stable when the last sublevel is filled with electrons as S 2 P 6 d 10 F 14, The last sublevel is half filled with electrons as P 3 d 5 F 7and the last sublevel is empty as d 0 F 0, Hund’s rule states that no electron paring takes place in a given sublevel until each orbital contains one electron.Įlectrons occupy the sublevel of lower energy first and then the higher energy, All elements in the same group are similar in properties, nP 6 is the zero group, d 6, d 7and d 8 are called group VIII, d 9 is called group I-B, d 10 is called group II-B, The long form periodic table is classified into four blocks: S-block elements Elements in zero-group are called noble gases: ( 2He, 10Ne, 18Ar, 36Kr, 54Xe, 86Rn), they are monoatomic and the electronic configuration of the outer sublevel in the noble gas is nP 6 except 2He (1S²), The maximum number of electrons which sublevels can take is S 2, P 6, d 10, F 14, The sequence of energy levels are:ġS<2S<2P<3S<3P<4S<3d<4P<5S<4d<5P<6S<4F<5d<6P<7S<5F<6d<7P
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