Answer
a. $1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2$
b. $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^4$
c. $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 5s^2$
Work Step by Step
We write the configurations with the subshells in principal number order (e.g., 3d comes before 4s, as in Table 28–4).
a. Z = 26 is iron.
$$1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2$$
b. Z = 34 is selenium.
$$1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^4$$
c. Z = 38 is strontium.
$$1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 5s^2$$
