Chapter 2.L2, Problem 1CT

Summary Introduction

To determine:

The type of bonds that the following elements will form, based on the octet rule:

N, S, C, P, O, H, Ca, Fe, Mg.

Introduction:

The octet rule is a chemical rule that is based on the observation that atoms of elements below the atomic number 20 tend to combine with other atoms in such a way so as to have 8 electrons in their outermost shell (valence shell).

Explanation of Solution

Nitrogen (N) has 7 electrons out of which 2 electrons are in the first orbital and 5 in the outermost orbital. These 5 valence electrons make N seek 3 more electrons to fill its orbital.

Sulfur (S) has atomic number 16 and the distribution of the 16 electrons in different orbitals is 2, 8, 6. The valence of S is 6 and S seeks two more electrons to fill its outer-most orbital.

The atomic number of Carbon (C) is 6 and the distribution of the 8 electrons in different orbitals is 2, 4. Thus, C has 4 valence electrons and it can either accept 4 electrons from another atom or donate four electrons to another atom to fill its outer-most orbital.

The atomic number of Phosphorus (P) is 15. The 15 electrons of P are distributed in different orbitals as 2, 8, 5. Thus, P has 5 valence electrons and it seeks 3 more electrons to complete its outer-most orbital.

Oxygen (O) has atomic number 8 and the distribution of these electrons in different orbitals is 2, 6. The valence of O is 6 and O seeks two more electrons to fill its outer-most orbital.

Hydrogen (H) has just one electron and it needs one more electron to complete its outer-most orbital.

Calcium (Ca) has 20 electrons that are distributed in different orbitals as 2, 8, 8, 2. Thus, Ca tends to donate its two valence electrons to acquire a state of filled outer-most orbital.

Iron has 26 electrons but when filling the orbitals by distributing 2, 8, 8, 8 electrons, it passes the third orbital that has d and p shells. It lacks 4 d-electrons and 6 p-electrons. Therefore, despite having a full octet, it can either give up the two electrons in 4s orbital or an additional pair of electrons in 3d orbital, making its valency either 2 or 3.

Magnesium (Mg) has 12 electrons that are distributed in different orbitals as 2, 8, 2. Therefore, Mg tends to give up its two valence electrons and assume a configuration of filled outer-most orbitals.

Conclusion

The number of electrons in the outer-most orbital of any atom determines its tendency and manner of forming bonds with other atoms.