BMS 150 Lecture Notes - Lecture 2: Valence Electron, Covalent Bond, Hydrogen Bond
13 Jan 2017
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Chapter 2: water and carbon - the chemical basis of life. * protons and neutrons are located int he nucleus. * electrons are found in orbitals surrounding nucleus. * most of an atom"s volume is empty space. * electrons move around atomic nuclei in speci c regions called orbitals. Each orbital can hold dup to two electrons. * orbitals are grouped into levels called electron shells. Electron shells are numbered, with smaller numbers closer to nucleus. Electrons in outermost shell are called valence electrons. * elements commonly found in organisms have at least one unpaired valence electron. The number of unpaired electrons in an atom is its valence. * most abundant elements found in organisms: carbon, nitrogen, oxygen, sodium, magnesium, phosphorus, sulphur, chlorine, hydrogen. Un lled electron orbitals allow formation of chemical bonds and atoms are most stable when each electron orbital is lled. Covalent bond: each atom"s unpaired valence electrons are shared by both nuclei to.
