CH 221 1st Edition Lecture 2 Outline of Last Lecture I. Course ObjectivesII. Meaning of Organic Chemistrya. Components of Organic Chemistryb. Applications of Organic Chemistry Outline of Current Lecture III. Structure of an Atoma. ElectronsIV. Isotopes of CarbonV. Carbon OrbitalsVI. Distribution of ElectronsVII. Orbital RulesVIII. Carbon, Nitrogen, and Oxygen Distributiona. Octet Ruleb. HydrogenIX. BondingCurrent LectureIII. Atoms have very small diameters (~2x10^-10m or 200 pm) with very dense nuclei (10^-15m) composed of:- Protons (positive charge)- Neutrons (neutral charge)a. Electrons are negatively charged and are located in the space surrounding the nucleus, remindful of a cloud.Atoms are similar to onions in that they contain shells (layers) on which electrons lie.IV. Isotopes of Carbon have the same atomic number but contain a different number of neutrons.- Atomic number (z) is the number of protons in the nucleus.- Mass number (A) is the number of protons plus the number of neutrons.-SymbolzAC612 C613 C614These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Carbon- Group 4A element therefore can share 4 valence electrons in 4 covalent bonds.V. Carbon Orbitals- Four different kinds of orbitals denoted as; s p d f- s and p are the most important orbitals in organic and biological chemistry- s orbitals- spherical, nucleus at center- p orbitals- dumbbell shaped, nucleus in the middle of lobesVI. Distribution of ElectronsFirst Shell Second Shell Third ShellAtomic Orbitals s s p s p d# of Atomic Orbitals 1 1, 3 1, 3, 5Max. Number of Electrons 2 8 18- First shell is closest to the nucleus- The closer the atomic orbital is to the nucleus, the lower the energy- Within a shell, s < p, meaning s is lower energy than pRelative energies of atomic orbitals:Low energy 1s < 2s < 2p < 3s < 3p < 3d High energyVII. Rules of Orbitals1. Aufbau Principle- an electron will go into the atomic orbital at the lowest energy2. Pauli Exclusion Principle- no more than two electrons can inhabit an orbital3. Hund’s Rule- an electron will go to an empty orbital before pairing up with other electronsOutermost shells= valence shell involved with all bondingEx. Oxygen’s valence electrons 2s2 2p4VIII. Carbon, Oxygen, and Nitrogen Distribution- Atoms to the left of carbon give up electrons- Atoms to the right of carbon accept electronsa. Octet RuleAn octet means having 8 valence electrons. This is associated with the stability of the noble gases. Atoms form octets to become more stable by losing, gaining, or sharing electrons in ionic or covalent bondsb. Hydrogen ExceptionHydrogen is content with only 2 valence electrons and can either lose or gain an electronin order to complete an octet.IX. Bonding- Ionic bonding is between ions of opposite charges (ex NaCl)- Covalent bonds are formed by sharing electrons- Nonpolar covalent bonds mean bonded atoms are the same- Polar covalent bonds mean bonded atoms are different- Oxygen forms two covalent bonds- Nitrogen forms three covalent bonds- Carbon forms four covalent bonds- There can also be nonbonding electrons or lone pair electrons (ex. nitrogen atom in
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