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. Identify these atoms and write their ground-state configurations.

(c) 1s²2s²2p⁶4s¹
(d) [Ar]4s¹3d¹⁰4p⁴
(e) [Ne]3s²3p⁴3d¹

Answer 1

Refer to the attached photo.

Parts c-e have been answered in the above attached photos.

Do note a brief explanation of the answers.

1). The orbital filling diagram attached explains the order in which the orbitals are to be filled.

2). In the question, there is an explicit mention of exciting of electrons within the atom. Hence NO ion states are formed in any of the given parts.

3). Given the excited atom configuration, it is very easy to predict the actual ground state configuration by checking the configuration wrt the orbital filling diagram.

In part c). we have 4p1 before 3p are even filled. The electron in 4p cant be filled in 2s or 2p as both are completely occupied. Hence, the electron belongs to 3p in the ground state.

In part d). the 4s orbital is missing an electron. The electron has been excited to 4p, which according to the orbital filling diagram comes AFTER 4s has been filled. hence one electron from 4p belongs to 4s (REFER the attached photo)

In part e). 3p is incomplete and 3d is filled with 1 electron. It is very clear that this electron belongs in 3p.

4). After the ground state configurations are obtained, all that is left is finding out the atomic number and checking the corresponding value in the perodic table.

Do let me know in the comment section if you are confused about the answer. I will be very glad to help you out.