Chapter 7.2, Problem 18LC

Interpretation Introduction

Interpretation: The electron configurations for two principal ions in body fluids need to be determined.

Concept introduction: The electron configuration explains the electron distribution in atomic orbitals. There is a standard notation to write an electron configuration. The atomic shell is written in a sequence with the number of electrons in superscript.

Answer to Problem 18LC

  ${\text{Na}}^{+}=1s^{2}2s^{2}2p^6$

  ${\text{Cl}}^{-}=1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Explanation of Solution

The extracellular fluid is composed of different cations and anions. The two principal ions are sodium and chloride ions. Here, sodium is a metallic element. It belongs to group 1 thus; it has 1 valence electron. Sodium can lose this electron to complete its octet. The ion so formed will have a positive charge and represented as ${\text{Na}}^{+}$ . The atomic number of Na is 11 thus, its electronic configuration can be represented as follows:

  $\text{Na}\left(11\right)=1s^{2}2s^{2}2p^{6}3s^1$

Now, the electronic configuration of sodium ion can be represented as follows:

  ${\text{Na}}^{+}=1s^{2}2s^{2}2p^6$

Similarly, chlorine is a non-metal. It belongs to group 17 with 7 valence electrons. It can gain 1 electron to attain noble gas electronic configuration. The ion so formed is ${\text{Cl}}^{-}$ . The atomic number of chlorine is 17 thus, its electronic configuration can be represented as follow:

  $\text{Cl}\left(17\right)=1s^{2}2s^{2}2p^{6}3s^{2}3p^5$

Now, the electronic configuration of chlorine ion can be represented as follows:

  ${\text{Cl}}^{-}=1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Conclusion

Thus, the electron configurations for two principal ions in body fluids are as follows:

  ${\text{Na}}^{+}=1s^{2}2s^{2}2p^6$

  ${\text{Cl}}^{-}=1s^{2}2s^{2}2p^{6}3s^{2}3p^6$