Question

Write electron configurations for a. the cations ${\mathrm{Sr}}^{2+},{\mathrm{Cs}}^{+},{\mathrm{In}}^{+}$, and ${\mathrm{Pb}}^{2+}$. b. the anions ${\mathrm{P}}^{3-},{\mathrm{S}}^{2-}$, and ${\mathrm{Br}}^{-}$.

Short answer

a. Electron configurations for the cations - ${\mathrm{Sr}}^{2+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}4d^0$$ - ${\mathrm{Cs}}^{+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^6$$ - ${\mathrm{In}}^{3+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}4d^{10}$$ - ${\mathrm{Pb}}^{2+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{0}4f^{14}5d^{10}$$ b. Electron configurations for the anions - ${\mathrm{P}}^{3-}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^6$$ - ${\mathrm{S}}^{2-}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^6$$ - ${\mathrm{Br}}^{-}$: $$1s{s}^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^6$$

Step-by-step solution

Step 1.1: Identify atom and charge for the first cation/anion

Note down the atom and its charge for the first cation or anion in the list. We'll start with the cation ${\mathrm{Sr}}^{2+}$. ##Step 2: Determine Atomic Number##

Step 2.1: Determine atomic number for the first cation/anion

Use the periodic table to find the atomic number of the atom. The atomic number of Sr (strontium) is 38. ##Step 3: Write Electron Configuration##

Step 3.1: Write electron configuration for the first neutral atom

Use the periodic table to write the electron configuration for the neutral atom. The electron configuration of Sr is $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^0$$ ##Step 4: Adjust Electron Configuration##

Step 4.1: Adjust electron configuration for the first cation/anion

Since Sr has a charge of +2, we need to remove 2 electrons from the electron configuration. Removing the electrons from the outermost shell, we get the electron configuration for ${\mathrm{Sr}}^{2+}$ as $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}4d^0$$ Follow the same steps for all cations and anions given in the exercise: a. Electron configurations for the cations - ${\mathrm{Sr}}^{2+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}4d^0$$ - ${\mathrm{Cs}}^{+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^6$$ - ${\mathrm{In}}^{3+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}4d^{10}$$ - ${\mathrm{Pb}}^{2+}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{0}4f^{14}5d^{10}$$ b. Electron configurations for the anions - ${\mathrm{P}}^{3-}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^6$$ - ${\mathrm{S}}^{2-}$: $$1s^{2}2s^{2}2p^{6}3s^{2}3p^6$$ - ${\mathrm{Br}}^{-}$: $$1s{s}^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^6$$