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Classification of Elements and Periodicity in Properties
On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
A principal quantum number is a number which determines the main energy level or shell in which the electron is present.It gives the average distance of the electron from the nucleus & specifies the value of the energy of the electron. The azimuthal quantum number is the number which determines the subshell in a principal energy shell to which an electron belongs.
In the periodic table of the elements, a period indicates the value of the principal quantum number (n) for the outermost shells. Each period begins with the filing of principal quantum number (n). The value of n for the sixth period is 6. For n = 6, azimuthal quantum number (l) can have values of 0, 1, 2, 3, 4.
According to Aufbau’s principle, electrons are added to different orbitals in order of their increasing energies. The energy of the 6d subshell is even higher than that of the 7s subshell.
In the 6th period, electrons can be filled in only 6s, 4f, 5d, and 6 p subshells. Now, 6s has one orbital, 4f has seven orbitals, 5d has five orbitals, and 6p has three orbitals. Therefore, there are a total of sixteen (1 + 7 + 5 + 3 = 16) orbitals available. According to Pauli’s exclusion principle, each orbital can accommodate a maximum of 2 electrons. Thus, 16 orbitals can accommodate a maximum of 32 electrons.
Hence, the sixth period of the periodic table should have 32 elements.
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How many elements are present in:
(i) second period
(ii) fourth period
(iii) sixth period?
What is the name given to the s-block elements?
To which block the element with outer electronic configuration 4s23d10 belongs?
Why are there 10 elements in each series of d-block?
In terms of electronic configuration,
what is common in a given period and group?
Give the general electronic configuration of
(i) Transition elements (ii) Inner transition elements.
Name the group and period to which an element with Z = 15 belongs ?
What are the advantages of periodic classification of elements?
In the modern periodic table, the period indicates the value of:
(a) atomic number
(b) atomic mass
(c) principal quantum number
(d) azimuthal quantum number.
Which of the following statements related to the modern periodic table is incorrect?
(a) The p-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in a p-shell.
(b) The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell.
(c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell.
(d) The block indicates value of azimuthal quantum number (l) for the last subshell that received electrons in building up the electronic configuration.
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