Question
The statement that is not correct for periodic classification of elements is
A.
the properties of elements are periodic function of their atomic numbers
B.
non-metallic elements are less in number than metallic elements
C.
for transition elements, the $$3d$$ orbitals are filled with electrons after $$3p$$ orbitals and before $$4s$$ orbitals
D.
the first ionization enthalpies of elements generally increase with increase in atomic number as we go along a period
Answer :
for transition elements, the $$3d$$ orbitals are filled with electrons after $$3p$$ orbitals and before $$4s$$ orbitals
Solution :
According to Aufbau principle, "in the ground state of the atoms, the orbitals are filled in order of their increasing energies." The increasing order of energy according to $$\left( {n + l} \right)$$ rule is : $$1s,2s,2p,3s,3p,4s,3d,4p,5s...$$ etc.
Therefore, the $$3d$$ orbitals are filled with electrons after $$4s$$ orbitals and before $$4p$$ orbitals.