Question

the electron configurations described in this chapter all refer to gaseous atoms in their ground states. an atom may absorb a quantum of energy and promote one of its electrons to a higher-energy orbital. when this happens, we say that the atom is in an excited state. the electron configurations of some excited atoms are given. select the configuration that would correspond to an excited state of n.
○ $1s^1 2s^1$
○ $1s^2 2s^2 2p^2 3d^1$
○ $1s^2 2s^2 2p^6 4s^1$
○ $\text{ar} 4s^1 3d^{10} 4p^4$
○ $\text{ne} 3s^2 3p^4 3d^1$

Explanation:

1. First, recall the ground - state electron configuration of nitrogen (N). The atomic number of N is 7, so its ground - state electron configuration is $1s^{2}2s^{2}2p^{3}$.
2. For an excited state, an electron is promoted from a lower - energy orbital to a higher - energy orbital.

• Option 1: $1s^{1}2s^{1}$ has only 2 electrons. The atomic number of N is 7, so this is not a valid configuration for N (excited or ground state).
• Option 2: The ground - state configuration of N is $1s^{2}2s^{2}2p^{3}$. In the configuration $1s^{2}2s^{2}2p^{2}3d^{1}$, one electron from the 2p orbital (which is a lower - energy orbital compared to 3d) has been promoted to the 3d orbital. This is a valid excited - state configuration for N as the total number of electrons is $2 + 2+2 + 1=7$, which matches the atomic number of N.
• Option 3: $1s^{2}2s^{2}2p^{6}4s^{1}$ has 9 electrons. The atomic number of N is 7, so this is not a configuration for N.
• Option 4: $[Ar]4s^{1}3d^{10}4p^{4}$ has electrons corresponding to an atomic number much larger than 7 (Ar has 18 electrons, plus $1 + 10+4 = 23$ more, total 41), so this is not for N.
• Option 5: $[Ne]3s^{2}3p^{4}3d^{1}$ has electrons corresponding to an atomic number larger than 7 (Ne has 10 electrons, plus $2 + 4+1 = 7$ more, total 17), so this is not for N.

Answer:

$1s^{2}2s^{2}2p^{2}3d^{1}$ (the second option: $1s^{2}2s^{2}2p^{2}3d^{1}$)