Question

15 б за наилучший ответ. Объясните мне пожалуйста что такое формула Льюиса. Подробно, как тупому чайнику.

Answer 1

What is Lewis Formula?

The Lewis formula, also known as the Lewis structure or electron dot structure, is a way to represent the bonding and non-bonding electrons in a molecule or ion. It was developed by the American chemist Gilbert N. Lewis in the early 20th century.

In a Lewis formula, the chemical symbol of an element represents its atomic nucleus and any inner-shell electrons. The valence electrons, which are the electrons involved in chemical bonding, are represented as dots around the symbol. Each dot represents one valence electron.

Lewis formulas are used to understand the bonding patterns and predict the molecular geometry of molecules. They provide a visual representation of how atoms are connected and how electrons are shared or transferred between atoms.

How to Draw Lewis Formulas?

To draw a Lewis formula, follow these steps:

1. Determine the total number of valence electrons for all the atoms in the molecule or ion. The valence electrons are the electrons in the outermost energy level of an atom.

2. Identify the central atom, which is usually the least electronegative atom or the one with the highest valence.

3. Connect the central atom to the surrounding atoms using single bonds. Each single bond represents two electrons.

4. Distribute the remaining electrons around the atoms to satisfy the octet rule. The octet rule states that atoms tend to gain, lose, or share electrons to achieve a stable electron configuration with eight valence electrons.

5. If there are still remaining electrons, place them as lone pairs on the outer atoms or the central atom, if necessary.

6. Check if all atoms have an octet of electrons, except for hydrogen, which only needs two electrons. If any atoms lack an octet, form multiple bonds by converting lone pairs into bonding pairs.

7. Finally, count the total number of electrons used in the Lewis formula to ensure it matches the total number of valence electrons determined in step 1.

Example of Drawing a Lewis Formula

Let's take the example of water (H2O) to illustrate how to draw a Lewis formula:

1. Hydrogen (H) has 1 valence electron, and oxygen (O) has 6 valence electrons. So, the total number of valence electrons is 2 (for hydrogen) + 6 (for oxygen) = 8.

2. Oxygen is the central atom in water.

3. Connect the oxygen atom to the two hydrogen atoms using single bonds:

   H - O - H
   

4. Oxygen has used 2 electrons (1 bond), and there are 6 electrons remaining.

5. Place the remaining 6 electrons as lone pairs on the oxygen atom:

   H - O : H
   

6. Oxygen now has a total of 8 electrons (2 bonds and 2 lone pairs), satisfying the octet rule. Hydrogen also has 2 electrons, which is its duet rule.

7. The total number of electrons used in the Lewis formula is 2 (from the bonds) + 6 (from the lone pairs) = 8, which matches the total number of valence electrons.

Conclusion

The Lewis formula is a visual representation of the bonding and non-bonding electrons in a molecule or ion. It helps chemists understand the structure and properties of compounds. By following the steps outlined above, you can draw Lewis formulas for various molecules and ions.