Question

What is the Lewis electron dot diagram of \(\mathrm{I}_{2}\) ? Circle the electrons around each atom to verify that each valence shell is filled.

Short answer

Each iodine in I2 shares one pair and has 3 lone pairs, fulfilling the octet rule.

Step-by-step solution

Determine the number of valence electrons

Iodine (I) is in Group 17 of the periodic table and has 7 valence electrons. Since the molecule I2 consists of two iodine atoms, the total valence electrons initially available are 14 (7 from each iodine).

Draw a skeleton structure

Sketch the skeletal structure for I2: I - I. Place one pair of electrons (a single bond) between the atoms to form the bond and make sure to note that each iodine atom is initially bonded by sharing one pair of electrons.

Distribute remaining valence electrons

After forming the single bond between the iodine atoms, count the used electrons: 2 electrons are used for the bond. Subtract these from the total, leaving 12 electrons (14 - 2 = 12) to be distributed as lone pairs on each iodine atom.

Assign lone pairs to each atom

Distribute the remaining 12 electrons as lone pairs around each iodine atom ensuring that each atom follows the octet rule. This results in placing 6 electrons (3 pairs) as lone pairs around each iodine atom.

Verify octet fulfillment

Check each iodine atom to ensure they fulfill the octet rule: each iodine should have 8 valence electrons, which includes 6 in lone pairs plus 2 shared in the bond. Circle the lone pairs and shared electrons around each iodine atom to indicate their electron participation.

Key concepts

Valence Electrons

Valence electrons are the electrons present in the outermost shell of an atom. These electrons play a crucial role in chemical bonding because atoms usually tend to gain, lose, or share electrons to complete this outer level. This completion often means achieving a stable electron arrangement similar to the nearest noble gas.

• For iodine, which is in Group 17 of the periodic table, there are 7 valence electrons. This is because it is placed in the 7th column of the p-block elements, and both the s and p sublevels of its outermost shell are filled with these electrons.
• In a molecule of iodine ( I_2 ), each iodine atom contributes these 7 valence electrons, making a total of 14. This number is essential for determining the Lewis structure of I_2 .

Understanding how to count and use these electrons is key to predicting how an atom bonds with another since only valence electrons are involved in the formation of bonds and in Lewis structures.

Iodine Molecule

The iodine molecule, scientifically represented as I_2 , consists of two iodine atoms bonded together. This diatomic molecule works as a perfect example for illustrating the principles of chemical bonding through the Lewis electron dot structure.
For iodine atoms, the Lewis electron dot diagram starts by placing one pair of electrons between the iodine atoms to form a covalent single bond. This shared pair of electrons signifies the bond between the atoms.

• After establishing the bond, we count the remaining valence electrons. Initially, there are 14 valence electrons available (7 from each iodine atom). Since 2 are involved in the bonding, we are left with 12 electrons.
• These remaining electrons are distributed as lone pairs around each iodine atom to fulfill the octet rule, ultimately placing 3 lone pairs (6 electrons) around each atom.

The Lewis structure for I_2 helps visualize how the two iodine atoms share electrons and also maintain enough electrons around themselves to meet stability criteria.

Octet Rule

The octet rule is a fundamental concept in chemistry stating that atoms tend to form bonds resulting in eight electrons in their valence shell. This rule stems from the observation that elements become stable by attaining an electron configuration similar to that of the noble gases.
For iodine, achieving an octet means configuring its valence electrons to fill the outer shell completely, often by sharing electrons with another atom. In the case of the iodine molecule, each iodine atom attains stability by:

• Sharing one pair of electrons, forming a single covalent bond between the two iodine atoms, which adds 2 more electrons to each atom's environment.
• Acquiring three lone pairs of electrons (6 electrons) each, completing the 8-electron array around each iodine atom.

The verification of this rule can be seen in the Lewis structure where each atom in I_2 appears to be content, fully surrounded by electrons. Observing the octet rule in practice helps in understanding the nature of chemical stability in molecules.