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Which of the following sets of quantum numbers is correct for an electron in $$4f$$ orbital?
For an electron in a $$4f$$ orbital, the quantum numbers must satisfy the following conditions.
The principal quantum number, $$n$$, is given by the shell number. Since the electron is present in the fourth shell,
$$n=4$$
The azimuthal quantum number, $$l$$, depends on the type of orbital:
$$s \rightarrow l=0$$
$$p \rightarrow l=1$$
$$d \rightarrow l=2$$
$$f \rightarrow l=3$$
Since the electron is in an $$f$$-orbital,
$$l=3$$
The magnetic quantum number, $$m_l$$, can have values from $$-l$$ to $$+l$$.
For $$l=3$$,
$$m_l=-3,-2,-1,0,+1,+2,+3$$
Hence, any value outside this range is not possible.
The spin quantum number, $$m_s$$, can have only two values:
$$m_s=+\frac{1}{2}\ \text{or}\ -\frac{1}{2}$$
Checking option (C):
$$n=4,\ l=3,\ m_l=+1,\ m_s=+\frac{1}{2}$$
All these values satisfy the allowed conditions for a $$4f$$ electron.
Therefore, the correct set of quantum numbers is
$$n=4,\ l=3,\ m_l=+1,\ m_s=+\frac{1}{2}$$
Hence, option (C) is the correct answer.
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