Chemical Bonding - Unit 4

Chemical Bonding - Unit 4

• Bonding is a theoretical concept based on indirect empirical evidence and logical reasoning.
• The key question is: how does bonding affect material properties?
• Students should follow procedures at the designated station to create slime.
• Compare slime properties with other groups.
• Discuss the science behind slime formation and the role of bonding.

Types of Polymers

• Polymers include nylon, polyester, polyethylene, and PVC.
• Examples of polymer usage are clothing and plastic containers.

Why Study Bonding Theory?

• Bonding theory helps explain the structures of various substances as well as explaining chemical reactions.
• Explains physical and chemical properties.
• Discusses breaking and forming chemical bonds.

Molecular Models

• Students should be able to determine the formula, name, number and types of bonds, and shape of molecules.
• Visual representations are useful for understanding molecular shapes.

What is a Bond?

• A bond describes the electrostatic attraction between two particles.
• Valence electrons play a crucial role in bonding.

Intramolecular Bonds

• Intramolecular bonds refer to the bonds within a molecule.
• Bonds exist between atoms.

Number of Bonds

• Only valence electrons are involved in bonding.
• Electrons in lower energy levels are held tightly by the nucleus.
• Magnesium (Mg) provides a common example for valence electron determination using Bohr diagrams. (First energy level = 2 electrons; Second energy level = 8 electrons; Third energy level (valence) = 2 electrons).

Valence Electrons

• Determine the number of electrons in the valence energy level for various elements (Na - 1; Ca - 2; Al - 3; C - 4; P - 5; O - 6, Cl - 7; Ar - 8).

Orbitals

• Orbitals define regions of space where electrons are likely to be found.
• There are four orbitals within the valence energy level.

Octet Rule

• Each valence orbital can hold 0, 1, or 2 electrons.
• The maximum number of electrons in the valence level is 8.

Exceptions to the Octet Rule

• Hydrogen (H) and Helium (He) are exceptions, with a maximum of 2 valence electrons.

Lewis Electron Dot Symbols

• Provide a simple 2D representation of complex 3D structures.
• Show the distribution of valence electrons. (Ex. Na, N, Cl).

How to Draw Lewis Dot Diagrams

• Use the atomic symbol for the element to indicate the nucleus and inner energy levels.
• Place dots around the symbol to represent valence electrons (e.g., C, I).
• Each orbital should have one dot before pairing up. (e.g., for 5th – 8th electrons).

Lone Pairs vs. Bonding Electrons

• Lone pairs are pairs of electrons.
• Bonding electrons are single electrons that can either be shared or transferred.
• The number of bonding electrons equals the number of bonds.

Bonding Capacity of Atoms

• Tabulated data shows how many valence electrons and bonding electrons are in common atoms (carbon, nitrogen, oxygen, halogens, hydrogen).

Workbook Practices

• Workbook practices are assigned for further application of understanding. (Practice #1, #2)

Bond Formation

• When atoms collide, their orbitals overlap.
• The nuclei of each atom tries to capture the valence electrons from the other atom.
• Electronegativity determines which atom "wins" the electron.

Electronegativity

• Electronegativity measures an atom's attraction for bonding electrons.
• Metals have low electronegativities, while non-metals exhibit high electronegativity values. (Metals tend to lose electrons, while nonmetals tend to attract electrons).
• The electronegativity value and difference determines the nature of a chemical bond.

Ranking Electronegativity

• Practice ranking atoms by electronegativity from lowest to highest. (Ex. Al, Cl, Ca, Ar)
• Fluorine is a special case due to an already full octet after gaining an electron.

Bond Type Determination

• Differences in electronegativity values determine the type of bond. Different types include: (covalent (polar/non-polar), ionic, metallic).

Covalent Bonds (Types)

• Covalent bonds exist in molecular compounds.
• High/similar electronegativities are key characteristics.
• Covalent bonds involve sharing of bonding pairs of electrons.
• Two main types include: -Non-polar (electronegativity values are equal) and -Polar covalent (difference in electronegativity is less than 1.7).

Ionic Bonds

• The presence of a large difference in electronegativity values (greater than or equal to 1.7) is a characteristic for an ionic bond.
• The atom with higher electronegativity can remove electrons from the atom with lower electronegativity.
• The removal leads to ions forming.

Metallic Bonds

• Metals exhibit low/similar electronegativity values when forming metallic bonds.
• Metals have a tendency to give up their valence electrons.
• A "sea" of shared electrons creates a metallic bond.

Properties of Metals Explained by Metallic Bonding

• Malleability and ductility - layers of metal ions can slide past each other readily.
• Electrical conductivity - electrons are free to move.
• High melting points - strong attraction to the electron sea.

Explore the fundamental concepts of chemical bonding in this quiz focusing on molecular structures, bonding theory, and polymers. Understand how bonding influences material properties and dive into practical examples through slime creation and comparative discussions. Additionally, learn about various types of polymers and their applications.