2. Draw the appropriate number of electron shells and the appropriate number of

Question

electrons in each shell for phosphorus. The nucleus of the atom is below9. Hint:
Phosphorus has 15 electrons.
6. Octet Rule
a. Atoms are most stable and least likely to bond with other atoms when their
outermost electron shell is filled to capacity.
b. The number of vacancies in the outermost shell determines if and how an
atom will bond with other atoms.
c. Explain why the atom is stable when the outermost electron shell is full.

Answer 1

Electron Shells and Electrons for Phosphorus

Phosphorus (P) has 15 electrons, which are arranged in electron shells around its nucleus. The distribution of electrons across the various shells is as follows:

• 1st shell: Can hold a maximum of 2 electrons.
• 2nd shell: Can hold a maximum of 8 electrons.
• 3rd shell: Can hold a maximum of 18 electrons, but for phosphorus, it holds only 5 electrons because phosphorus has a total of 15.

Electron Configuration:

• 1st shell: 2 electrons
• 2nd shell: 8 electrons
• 3rd shell: 5 electrons

Representation:

Below is a simple representation of phosphorus with its nucleus and electron shells:

         3rd shell
          ↑ ↑ ↑ ↑ ↑
         ---------------
        |       P       |
         ---------------
         2nd shell
       ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑
      ----------------------
     |        8        |
      ----------------------
      1st shell
     ↑ ↑
    ---------
   |    2    |
    ---------

Octet Rule Explanation

a. Stability of Atoms:

Atoms are most stable when their outermost electron shell (also known as the valence shell) is filled to capacity. This is known as the octet rule, which states that atoms tend to form bonds in such a way that they each have eight electrons in their valence shell, achieving an electron configuration similar to the nearest noble gas.

b. Vacancies in the Outermost Shell:

The number of vacancies (available spaces) in the outermost shell significantly influences how an atom bonds with other atoms. If an atom has:

• Full valence shell: It is generally stable and does not readily bond with other atoms.
• One or more vacancies: It tends to engage in chemical reactions or bond with other atoms to fill its outer shell and achieve a more stable configuration.

c. Stability with a Full Outermost Shell:

An atom is considered stable when its outermost electron shell is full because:

• The filled shell configuration lowers the overall energy of the atom, making it less reactive and more stable.
• Atoms strive to reach a state of minimum energy, and a filled valence shell represents a lower energy state.
• This stability reduces the tendency of atoms to lose, gain, or share electrons, leading to fewer reactions or interactions with other atoms.

In summary, atoms with full outermost shells exhibit a lower energy state, making them less reactive and more stable compared to those with vacancies in their outer shells. This principle explains the behavior of elements in terms of bonding and chemical reactivity.