CHEM261 Lecture 1: Lesson 1.pdf
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CHEM261 Full Course Notes
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Atom: the majority of the mass of an atom is in the nucleus. But the electrons are the business end of the atom. Atomic structure orbitals: electrons are directly involved in bonding. The overlap of electrons from two different atoms forms a bond: electrons are arranged around the nucleus in shells. The first two shells are the most important in organic chemistry. Lecture notes 1: shell 1 is closer to the nucleus than shell 2 and therefore electrons in first shell are more strongly held (more effective positive/negative attraction) than those in the second shell. Impossible to determine exactly where the electron is. Quantum mechanics tells us only the probable regions: each atomic orbital holds a pair of electrons, shapes of s and p atomic orbitals, the ones of most importance in organic chemistry, are shown below. s orbital. Nitrogen, has five valence electrons (2 in 2s shell and 3 in 2p shell)
