In a chromium atom,the number of electrons which have $n = 2$ and $l = 1$ is:

The four quantum numbers for the valence shell electron or last electron of sodium $(Z = 11)$ are:

The quantum numbers $+1/2$ and $-1/2$ for the electron spin represent

Total number of unpaired electrons in an atom of atomic number $29$ is

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

The atomic number of an element is $35$ and its mass number is $81$. The number of electrons in the outermost shell is: