BIOLOGY 172 Lecture Notes - Lecture 3: Valence Electron, Electron Shell, Hydrogen Bond

• School: U of M
• Department: Biology
• Course: BIOLOGY 172
• Professor: Matthew Chapman

Document Summary

Chemistry basics/macromolecules: atoms: basic unit of matter. Electrons are in orbitals surrounding nucleus from a distance: protons = electrons in order to particle to be neutral, elements. Atoms with same atomic number have the same chemical properties and belong to the same element. Forms of element with different number of neutrons are isotopes. Mass number: protons + neutrons of most common isotope: electron arrangement. Electrons move around nuclei in orbitals: each orbitals can hold up to 2 electrons. Ii) orbitals are grouped into levels called electron shell. Iv) electrons in the outermost shell valence electrons: # of unpaired electrons in an atom is its valence (common elements found in organisms typically have 1 unpaired valence electron. Vi) atoms are most stable when each orbital has 2 electrons: covalent bonds: atoms share pairs of valence electrons. Polar covalent bonds: electrons are not shared equally, so for a water molecule there are partial charges on opposite sides: oxygen is a good example.