Fundamentals of Atomic Structure and Chemical Bonding

1. CHAPTER 1STRUCTURE DETERMINES PROPERTIES

2. ATOMIC STRUCTURE • number of protons determines the element • combinations are possible, with a constant number of protons but varying number of neutrons - ISOTOPES Chapter 1: Introduction and Review

3. ORBITALS AND SYMMETRY Chapter 1: Introduction and Review

4. THE BUILDING OF THE ELECTRONIC CONFIGURATION OF ATOMS • A maximum of two (2) electrons can be placed in any single orbital (The Pauli’s exclusion principle) • Electronic states are occupied in order of increasing energy. • Degenerate states (of equal energy!) are first all single occupied (The Hund’s rule).

5. Lewis’ Octet Hypothesis • Atoms will enter into chemical reactions and form bonds with the principle goal to achieve octet configurations of their valence shells

6. ELECTRONEGATIVITY – PAULING’S SCALE Chapter 1: Introduction and Review

7. RULES FOR LEWIS STRUCTURES • Count the total number of electrons available (A) • Calculate the total number of necessary electrons (B), in • order for each atom to achieve an octet (Hydrogen needs • only two electrons!!) • Subtract and divide: (B – A)/2 = number of bonds • Construct a meaningful structure with the above calculated • number of bonds • If electrons remain, first assign lone pairs to the terminal • atoms, then to the central atoms, wherever necessary • Do not forget: Hydrogens are ALWAYS terminal! Chapter 1: Introduction and Review

8. RESONANCE STRUCTURES • A resonance structure is acceptable if: • it is a meaningful Lewis structure (Please refer to rules for writing Lewis structures!) • electrons are moved but the skeleton of the molecule is retained • A resonance structure has a greater importance if: • it contains a greater number of bonds and atom octets • it has minimum charge separation • the negative charge resides on a more electronegative atom Chapter 1: Introduction and Review

9. COMMON BONDING PATTERNS Chapter 1: Introduction and Review