Introduction to Chemical Bonding and Valence Electrons

Valence Electrons of Hydrogen

  • Number of Valence Electrons

    • Hydrogen has 1 valence electron.

    • Every hydrogen atom has 1 valence electron.

  • Valence Electrons Desired

    • Hydrogen desires 2 valence electrons to achieve stability (like Helium).

    • With 2 valence electrons, hydrogen is stabilized and exhibits similar characteristics to the noble gas Helium, which is inherently stable.

  • Covalent Bonding

    • Rather than gaining or losing an electron, two hydrogen atoms can approach each other and share their valence electrons.

    • This sharing of electrons is defined as covalent bonding.

    • By sharing, each hydrogen effectively has 2 valence electrons:

    • Shared Electrons = 2

    • Conclusion: This sharing satisfies each hydrogen atom.

  • Bond Representation

    • Bonds are represented by a dash (-) indicating the shared pair of electrons.

    • Each bond contains 2 electrons.

    • General rule: All covalent bonds consist of 2 electrons.

Carbon and Its Valence Electrons

  • Valence Electrons in Carbon

    • Carbon has 4 valence electrons.

  • Definition of Valence

    • Valence refers to the outermost shell of electrons in an atom.

    • Notably, the valence shell is distinct from inner shells, which contain other electrons.

  • Octet Rule

    • Carbon aspires to achieve a total of 8 valence electrons to be stable (similar to the nearest noble gas).

    • This stability is governed by the octet rule.

    • Since carbon possesses 4 electrons, it needs an additional 4 to reach 8.

  • Formation of Bonds

    • Each electron desired corresponds to a bond formed. Thus, since carbon requires 4 additional electrons, it will form 4 bonds.

Valence Electrons in Nitrogen, Oxygen, Fluorine, and Neon

  • Valence Electrons in Nitrogen

    • Nitrogen has a total of 7 electrons:

    • Valence Electrons: 5

    • Nitrogen needs 3 more electrons to satisfy the octet rule.

    • Therefore, nitrogen will form 3 bonds.

  • Valence Electrons in Oxygen

    • Oxygen has 6 valence electrons.

    • Oxygen will form 2 bonds since it requires 2 additional electrons for stability.

  • Valence Electrons in Fluorine

    • Fluorine has 7 valence electrons and will form just 1 bond to reach 8.

  • Valence Electrons in Neon

    • Neon has 8 valence electrons.

    • As a noble gas, neon is stable; thus, it does not form any bonds (0 bonds).

Molecular Bonding

  • Nonmetals

    • Compounds formed primarily from nonmetals are categorized as molecular compounds.

    • Covalent bonds are the means by which these nonmetal atoms bond.

  • Covalent Definition

    • Covalent means to share electrons among atoms to form stable molecules.

  • Valence Electron Calculations

    • For creating Lewis diagrams:

    1. Count total valence electrons.

    2. Draw a skeleton influenced by single bonds.

Example: Hydrogen Chloride (HCl)

  1. Valence Electrons

    • Hydrogen has 1 valence electron.

    • Chlorine possesses 7 valence electrons (total of 17 in its atomic structure).

    • Therefore: Total = 1 (H) + 7 (Cl) = 8 avialable valence electrons.

  2. Skeleton Structure

    • Draw a single bond between H and Cl using 2 electrons, represented as a dash.

    • Remaining electrons (6) will be allocated around chlorine, resulting in 3 lone pairs:

      • H is satisfied with 2 electrons.

      • Cl has to accommodate 3 lone pairs as well as the bonding pair.

  3. Bonding and Lone Pairs

    • The pair of electrons between H and Cl forms a bonding pair, while the trio of pairs on Cl becomes lone pairs.

Electron Requirements of Nonimetal Compounds

  • Summary

    • Hydrogen makes 1 bond (satisfied with 2 electrons).

    • Halogens have 7 valence electrons, each requiring 1 bond to reach stability.

Lewis Structures for Various Compounds

  1. Oxygen ()

    • 6 valence electrons form 2 bonds in O₂ (each oxygen atom bonding with another).

  2. Nitrate (NO₃⁻)

    • Each nitrogen requires 3 bonds. Calculation yields incorporation of 10 valence electrons.

  3. Water

    • Oxygen requires 2 bonds and satisfies hydrogen’s need for 1 bond.

Steric Number Concept

  • Definition

    • The steric number is classified as the count of total bonding and lone electron pairs around the central atom.

  • Calculation Examples

    • Methane (CH₄)

    • Steric number: 4 (no lone pairs). Shape: Tetrahedral.

    • Water (H₂O)

    • Steric number: 4 (2 lone pairs). Shape: Bent/Angular.

  • General Observation

    • For central atoms, the need and capacity to bond can vary markedly, leading to diverse molecular geometries based on steric configurations and electron distributions.

Conclusion

  • This summary highlights the principles underlying molecular formation, bond creation, and electron distribution, all fundamental to understanding chemical bonding in nonmetals and organic compounds.