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Topic 2: Bonding & Properties, Bonding & Properties - Coggle…
Topic 2: Bonding & Properties
Atomic Fundamentals
Nucleus component
Atomic number (Z): Number of protons
Neutron number (N): Number of neutrons
Atomic Mass (A) = Atomic number (Z) + Neutron number (N)
Subatomic particles
Neutron
Mass: 1.675 x 10^-24 g ; Charge: 0 C
Electron
Mass: 9.109 x 10^-28 g ; Charge: -1.602 x 10^-19 C
Proton
Mass: 1.673 x 10^-24 g ; Charge: +1.602 x 10^-19 C
Atomic measurements
Atomic Mass Unit (amu): 1/12 mass of C12 atom
Mole: 6.02 x 10^23 of atoms or molecules
Atomic Weight: Weighted average of isotopes
Mass Equivalence: 1 amu/atom = 1g/mole
Atomic Mass (A): Sum of nucleus protons and neutrons
Atomic Models
Bohr Atomic Model
Quantum Jump: Absorption or emission of energy
Energy States: Electrons occupy lowest available state
Quantized Energies: Specific allowed energy values
Discrete Orbitals: Electrons revolve in defined orbitals
Wave-mechanical Model
Electron Characteristics: Wave-like and particle-like
Electron Cloud: Probability distribution position
Quantum Numbers
Subsidiary Quantum Number (l): Shape of subshell (s, p, d, f)
Magnetic Quantum Number (ml): Number of energy states
Principal Quantum Number (n): Size and energy level shell (K, L, M, N)
Spin Quantum Number (ms): Spin orientation
Pauli exclusion principle:
Each electron state can hold no more than 2 electrons, which must
have opposite spins.
Stable electron configuration: have complete s and p subshells
The Periodic Table
Electronegativity: Ranges from 0.7 to 4.0
High electronegativity: Tendency to acquire electrons
Bonding & Properties
Bonding Force & Potential Energy
Repulsive Force (FR): Interaction between core electrons at close interatomic distance
Attractive Force (FA): Coulombic attraction between oppositely charged ions
Net Force Equation: FN = FA + FR
Equilibrium Spacing (ro): Distance where N = 0 and potential energy is minimized
Material Properties Correlation
Melting Temperature (Tm): Proportional to potential well depth (EO)
Modulus of Elasticity (E): Proportional to the slope of the force curve at ro
Thermal Expansion: Derived from asymmetry of the potential energy well
Primary Interatomic Bonds
Covalent Bonding
Mechanism: Electron sharing between adjacent atoms with small electronegativity difference
Directionality: Highly directional bonds
lonic Bonding
Mechanism: Electrostatic attraction between electropositive cations and electronegative anions
Directionality: Nondirectional bonding (magnitude equal in all directions)
Properties: Hard, brittle, electrically and thermally insulative
Metallic Bonding
Mechanism: Delocalized valence electron cloud ("sea of electrons") surrounding ion cores
Properties: High electrical and thermal conductivity, ductility
Secondary Bonding (Van der Waals & Hydrogen)
Physical Mechanism: Electric dipoles arising from separation of positive and negative portions
Binding Energy: Typically low, in the order of 10 kJ/mol (0.1 eV/atom)
Secondary Bonding (Van der Waals & Hydrogen)
Universal Presence: Exists between virtually all atoms or molecules
Hydrogen Bonding: Strong secondary bond between hydrogen and highly electronegative elements