BIOL 1441 1ST Edition Lecture 2 Outline of Last Lecture I. Structure II. Energy III. Chemical propertiesOutline of Current Lecture I. Bonds Current LectureI. Bonds i. Unpaired electrons=reactiveii. Combine other atoms to fill valence shellsiii. 3 main types:1. covalent: strongest (like marriage)2. ionic: positive and negative chill next to each other (dating)3. hydrogen: weakest (one night standa. covalent bonds:i. pair of valence electrons is shared1. orbitals overlapii. molecule: 2 or more atoms held together by a covalent bondiii. compound: consists of 2 or more different atoms1. water moleculeiv. single covalent bond: (hydrogen molecule)-share 1 electron1. H-----Hv. Double covalent bond: (oxygen molecule)1. O===Ovi. Bonding capacity: valence1. Valence: number of electrons it takes to fill the valence shell. (periodic table trick)vii. Nonpolar covalent bond: electros are shared equally-no charge (2 atoms of the same element)These 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.viii. Polar covalent bond: electrons NOT shared equally-charged (water molecule)ix. Electronegativity: attraction of an atom for the electrons in a covalent bond (CANT CHANGE)1. The more electronegative an atom, more strongly it pulls shared electrons to itselfa. Oxygen and nitrogen=very electronegativeHigh electronegativity- Oxygen- NitrogenLow electronegativity- Carbon- HydrogenNon-polar - O—O- N—N- C—C- H—H- C—H Polar - O—C- O—H- N—C- N—H - water molecule molecule (H2O)o Delta- partial charge(δ)b. Ionic bonds: between oppositely charged molecules or atomsi. Ion: charged atom or molecule = lose/gain electronii. More electronegative atom strips an electron completel away from another making it an ion1. Lose electron – positive charge (cation)2. Gain electron – negative charge (anion)iii. TRANSFERRING THE ELECTRON IS NOT THE FORMATION OF AN IONIC BONDiv. Transfer of electron creates two ionsv. Ionic compounds: salts1. In nature found as crystals, 3D lattice2. Only has a ratio of elementa. NaCl 1:1b. MgCl2 1:2c. NH4Cl 1:1c. Hydrogen bond: bond between polar moleculesi. Hydrogen atom covalently bonded to one electronegative atom in anoter polar covalent bondii. Easy to pull apart (to replicate)iii. Weak
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