Chem HW #13 - Chem HW #13 PDF

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Sofia Ferreira Mr. Baruch Chem HW #13 December 1st, 2016 Homework # 13: Pages 195-196 Questions 15-22 15. What is an ionic compound? In what form do most ionic compounds occur? An ionic compound is composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal. Most ionic compounds exist as crystalline solids. 16. What is a formula unit? What are the components of one formula unit of CaF2? A formula unit is the simplest collection of atoms from which an ionic compound’s formula can be established. CaF2 consists of one Calcium cation and two Fluorine anions. 17. What is lattice energy? In general, what is the relationship between lattice energy and the strength of ionic bonding? Lattice energy is the energy released when one mole of an ionic crystalline compound is formed from gaseous ions. The more lattice energy there is, the more the ionic bonds attracts electrons. 18. In general, how do ionic and molecular compounds compare in terms of melting points, boiling points, and ease of evaporation? What accounts for the observed differences in the properties of ionic and molecular compounds? Cite three physical properties of ionic compounds. Ionic compounds generally have higher melting and boiling points than molecular compounds and do not vaporize as easily at room temperature as molecular compounds do. The melting points, boiling points and ease of evaporation depend on how strongly its basic units are attracted to each other. Ionic compounds are hard, brittle, good conductors in the molten state. 19. What is a polyatomic ion? Give two examples of polyatomic ions. In what form do such ions usually occur in nature? A polyatomic ion is a charged group of covalently bonded atoms. Ammonium ion and Nitrate ion. Polyatomic ions combine with ions of the opposite charge to become ionic, they occur bonded to something. 20. How do the properties of metals differ from those of both ionic and molecular compounds? What specific property of metals accounts for their unusual conductivity? Metals differ from those of both ionic and molecular in their malleability and ductility. The freedom of motion of electrons in a network of metal atoms accounts for the high

electrical and thermal conductivity characteristic of all metals.

21. What properties of metals contribute to their tendency to form metallic bonds?

Metals easily remove their valence electrons and their electrons are able to move through their empty orbitals which causes metals to form a "sea of electrons”. 22. What is metallic bonding? How can the strength of metallic bonding be measured? Metallic bonding is the chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons. The strength of metallic bonding can be measured by the amount of heat required to vaporize the metal....