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Essential Elements

12 13 bondIng atomic stickiness Molecules are formed as atoms outer electrons share dances. Losing or gaining electrons causes atoms to become electrically charged ions. Most elements are either metals, which are electropositive, losing electrons to form cations, or nonmetals, which are electronegative and gain electrons to form anions. An ionic bond occurs when a negative anion borrows electrons from a positive cation to give them both full orbitals like the nearest noble gas top left opposite. Though tough and brittle with high melting points, many ionic compounds dissolve in water. Nonmetals combine using covalent bonds, which shuffle and share outer electrons into pairs, again filling up empty orbitals top right. The attraction felt by electrons for nucleii, outweighing their mutual repulsions, holds the resulting molecule together. In metallic bonds electrons float away from their nucleii, dissociating into a sea around a lattice of positive ions opposite. The conductivity and shininess of metals is due to these mobile electrons, and their strength and high melting points result from the lovestruck relationship between the ions and their mates. Hydrogen attached to a nonmetal pushes against unbonded lone pair electrons creating a slight charge across the molecule. If another electronegative atom is nearby, a weak hydrogen bond, vital in water and DNA, appears between them. With asymmetrical motions of electrons causing instantaneous small Van der Waals forces between atoms, and overlapping orbitals smearing bonds below right, atomic glues come in many forms.
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