Final answer:
The actual electron configuration of 2-7-1-1 represents a sodium atom in an excited state because it is at a higher energy level than its ground state configuration of [Ne]3s¹ (2-8-1).
Step-by-step explanation:
The actual electron configuration of sodium in an excited state represented by 2-7-1-1 indicates that sodium atoms are at a higher energy level than their ground state, which is 2-8-1. The excited state configuration is not the natural state of sodium, as its ground state electron configuration is [Ne]3s¹. The electron configuration you provided shows an electron has been promoted from the 3s orbital to a higher energy orbital, which is not typical for a stable sodium atom. Therefore, option a is correct as it represents sodium at a higher energy level than its ground state configuration of 2-8-1.
Option b is incorrect because sodium naturally is found in the 2-8-1 electron configuration, or more accurately, [Ne]3s¹. Option c is not correct as the configuration does not indicate the presence of a sodium isotope but an excited electron state. Option d is incorrect because sodium does not undergo spontaneous excitation; it requires energy input to reach an excited state.