In the sixth period,the orbitals that are filled are

The number of radial (spherical) nodes in a $4p$ orbital is $....$.

An ion with a charge of $-2$ has the electronic configuration $1s^2, 2s^2, 2p^6$. Identify the ion.

What is the number of unpaired electrons in a ferrous ion $(Fe^{2+})$?

Which of the following rules or principles states that "No two electrons in an atom can have the same set of four quantum numbers"?

Arrange the electrons represented by the following sets of quantum numbers in the decreasing order of energy.
$(i) \ n = 4, l = 0, m_l = 0, m_s = +\frac{1}{2}$
$(ii) \ n = 3, l = 1, m_l = 1, m_s = -\frac{1}{2}$
$(iii) \ n = 3, l = 2, m_l = 0, m_s = +\frac{1}{2}$
$(iv) \ n = 3, l = 0, m_l = 0, m_s = -\frac{1}{2}$