Question

1. write the electron-configuration notation for the element whose atoms contain the following number of electrons:

a. 3
b. 6
c. 8
d. 13

Explanation:

Step1: Follow Aufbau principle (lowest energy first)

Fill orbitals in order: $1s, 2s, 2p, 3s, 3p,...$; $s$ holds 2, $p$ holds 6 electrons.

Step2: Solve for 3 electrons

Fill $1s^2$, then 1 left in $2s^1$

Step3: Solve for 6 electrons

Fill $1s^2, 2s^2$, then 2 left in $2p^2$

Step4: Solve for 8 electrons

Fill $1s^2, 2s^2$, then 4 left in $2p^4$

Step5: Solve for 13 electrons

Fill $1s^2, 2s^2, 2p^6, 3s^2$, then 1 left in $3p^1$

Answer:

a. $1s^22s^1$
b. $1s^22s^22p^2$
c. $1s^22s^22p^4$
d. $1s^22s^22p^63s^23p^1$