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Across 2. the energy change occurring when separated gaseous ions are packed together to form an ionic solid. 5. the energy required to break a given chemical bond. 7. an electron pair found in the space between two atoms. 8. the distance between the nuclei of the two atoms connected by a bond, 9. the charge assigned to an atom in a molecule or polyatomic ion derived from a specific set of rules. 12. a condition occurring when more than one valid Lewis structure can be written for a particular molecule. 14. the three-dimensional arrangement of atoms in a molecule 15. ions containing the same number of electrons 17. a type of bond in which electrons are shared by atoms. 18. a bond in which one pair of electrons is shared by two atoms 19. a model whose main postulate is that the structure around a given model atom in a molecule is determined principally by minimizing electron-pair repulsions. 20. a diagram of a molecule showing how the valence electrons are arranged among the atoms in the molecule. 21. a property of a molecule whose charge distribution can be represented by a center of positive charge and a center of negative charge. 22. the electrostatic attraction between oppositely charged ions

Down 1. a model which assumes that a molecule is composed of atoms that are bound together by sharing pairs of electrons using the atomic orbitals of the bound atoms. 3. the tendency of an atom in a molecule to attract shared electrons to itself. 4. an electron pair that is localized on a given atom, an electron pair not involved in bonding. 6. is the energy of interaction between a pair of ions 10. a bond in which two pairs of electrons are shared by two atoms 11. a covalent bond in which the electrons are not shared equally because one atom attracts them more strongly than the other. 13. a bond in which three pairs of electrons are shared by two atoms 16. the observation that atoms of nonmetals tend to form the most stable molecules when they are surrounded by eight electrons (to fill their valence orbitals).