CHM102 Lecture Notes - Lecture 12: Ionic Bonding, Lone Pair, Electronegativity
Experimental Evidence about Electrons in Atoms
- Absorption and emission of energy by 1 mol of H atoms due to transitions of the
electron between n = 1 (ground state) and n = 2 stationary states.
- ΔE (for 1 mol) = (6.022 × 1023)(1.634 × 10−18) = 984 kJ
Electron Configurations in Atoms
- Order of assigning electrons to orbitals to achieve the ground-state configuration
(“aufbau” principle).
Electron Configurations
- The valence electrons of all the elements that belong to Groups 1 and 2 occupy
only s orbitals and these elements are called s-block elements.
- The elements in Groups 13−17 have partially filled p orbitals with valence
electrons and, along with Group 18, are called p-block elements.
Periodicity of Electron Configuration
- Particular chemical properties are attributed to the “outermost” (highest energy)
electrons, those that are most likely to interact when atoms come close to each
other.
- These outermost electrons are called valence electrons.
- Atoms of elements in the same group have similar ground-state valence electron
configurations.
Shielding and Effective Nuclear Charge
- How strongly are valence electrons attracted toward the nucleus?
- Valence electrons experience attraction with the nucleus but also repulsions from
other electrons.
- The effect of repulsion from other electrons in reducing the charge with the
nucleus is called shielding or screening.
- The resulting overall charge is called the effective nuclear charge (Z*).
Covalent Bonding of Molecules
- The bond is the net force of attraction composed of nucleus-electron attractions,
nucleus-nucleus repulsions, and electro-electron repulsions.
- Only valence electrons of one atom participate in bonding with other atoms of the
same molecule.
Document Summary
Absorption and emission of energy by 1 mol of h atoms due to transitions of the electron between n = 1 (ground state) and n = 2 stationary states. E (for 1 mol) = (6. 022 1023)(1. 634 10 18) = 984 kj. Order of assigning electrons to orbitals to achieve the ground-state configuration ( aufbau principle). The valence electrons of all the elements that belong to groups 1 and 2 occupy only s orbitals and these elements are called s-block elements. The elements in groups 13 17 have partially filled p orbitals with valence electrons and, along with group 18, are called p-block elements. Particular chemical properties are attributed to the outermost (highest energy) electrons, those that are most likely to interact when atoms come close to each other. These outermost electrons are called valence electrons. Atoms of elements in the same group have similar ground-state valence electron configurations.
