In a multi-electron atom, which of the following orbitals described by the three quantum numbers will have the same energy in the absence of magnetic acid and electric fields?

(a) n = 1, l = 0, m = 0
(b) n = 2, l = 0, m = 0
(c) n = 2, l = 1, m = 1
(d) n = 3, l = 2, m = 1
(e) n = 3, l = 2, m = 0

• (a) and (b)

• (b) and (c)

• (c) and (d)

• (d) and (e)

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.