Calcium fluoride, ionic bonding

Ionic compounds consist of positive ions (cations) and negative ions (anions) hence, ionic compounds often consist of a metal and nonmetal. The electrostatic attraction between a cation and anion results in an ionic bond that results in compound formation. Binary ionic compounds form from two elements. Sodium chloride (NaCl) and sodium fluoride (NaF) are examples of binary ionic compounds. Three elements can form ternary ionic compounds. Ternary compounds result when polyatomic ions such as carbonate (C032 ), hydroxide (OH-), ammonium (NH4+), form compounds. For example, a calcium ion, Ca2+, combines with the carbonate ion to form the ternary ionic compound calcium carbonate, CaC03. Molecular compounds form discrete molecular units and often consist of a combination of two nonmetals. Compounds such as water (H20), carbon dioxide (C02), and nitric oxide (NO) represent simple binary molecular compounds. Ternary molecular compounds contain three elements. Glucose ( 12 ) is a ternary molecular compound. There are several distinct differences between ionic and molecular compounds, as summarized in Table 1.2. 

Examine Figure 3.11. In an ionic bond, calcium tends to lose two electrons and fluorine tends to gain one electron. Therefore, one calcium atom bonds with two fluorine atoms. Calcium loses one of each of its valence electrons to each fluorine atom. Calcium becomes Ca2+, and fluorine becomes F . They form the compound calcium fluoride, CaF2. 

Solution The first two ions are single atom anions and are called sulfide and nitride. The next two are binary ionic compounds, calcium fluoride and potassium sulfide. The polyatomic ions hydroxide and sulfate are present in sodium hydroxide and sodium sulfate. Finally, the last two compounds are covalently bonded and are called sulfur trioxide and carbon tetrachloride. 

C Covalently bonded substances will use prefixes while ionic compounds will not. Choice A may seem correct, but a covalent compound s name does not start with the prefix mono-. Calcium fluoride is ionic and will not use prefixes at all. Tetra- is correct to indicate four in a covalently bonded compound. P is phosphorus and not potassium. Finally, Ti is titanium and not tin, Sn. 

You can see how electronegativity differences provide information about bond character. Think about the bonds that form between the ions sodium and fluoride and between the ions calcium and oxide. The electronegativity difference between Na and F is 3.1. Therefore, they form an ionic bond. The electronegativity difference between Ca and O is 2.4. They also form an ionic bond. However, the larger electronegativity difference between Na and F means that the bond between them has a higher percentage of ionic character. 

Calcium fluoride, CaF2 ionic ionic bonds 1,418°C... 

Insulating materials span a wide range from weakly van-der-Waals bonded molecular crystals to covalent crystals such as diamond or titanium dioxide to ionic crystals such as potassium bromide or calcium fluoride. Therefore, a general description of molecule-surface interactions is challenging in the case of insulating substrates. However, compared to metals, the interaction of organic molecules with... 

Figure 4.4 Simplified diagram of the ionic bonding in calcium fluoride, CaFj...

These terms are frequently used and may lead to confusion, if used in the wrong context. As a reminder, the valency of an atom is strictly the number of bonds (including o, n and 8) in which it participates in any particular compound. In IF , the iodine atom participates in seven a bonds to the fluorine atoms. The fluorine atoms are individually monovalent. Oxidation states are more useful than valency in describing ionic compounds. In the crystalline solid CaF0, the calcium is best thought of as composed of calcium dications and fluoride anions, Ca2+(F ),. The calcium is in its +2 oxidation state, having lost its valency electrons, and the fluorine atoms are in the -1 oxidation state, both having accepted an elec-... 

Draw diagrams to represent the bonding in each of the following ionic compounds a potassium fluoride (KF) b lithium chloride (LiCI) c magnesium fluoride (MgF2) d calcium oxide (CaO). 

---