Monatomic Ions with Noble-Gas Electron Configurations

1 Monatomic Ions with Noble-Gas Electron Configurations 

2 Identify the monatomic ions that are isoelectronic with a given noble-gas atom and write the electron configuration of those ions. 

You may wonder about the hydrogen ion, H+. This ion does not normally exist by itself, but rather exists as a hydrated hydrogen ion, which means that the hydrogen ion is associated with one or more molecules of water. This can be represented as 

Write the electron configurations for calcium and chloride ions. With what noble gases are these ions isoelectronic  

Lewis symbols use dots distributed around the symbol of an element to represent valence electrons. See Section 11,5. 

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Monatomic Ions with Noble-Gas Electron Configurations Ionic Bonds Covalent Bonds Polar and Nonpolar Covalent Bonds Multiple Bonds Atoms That Are Bonded to Two or More Other Atoms Exceptions to the Octet Rule Metallic Bonds... 

Figure 12.1 Monatomic ions with noble-gas electron configurations. Each color group includes one noble-gas atom and the monatomic ions that are isoelectronic with that atom. Beryllium and boron are not included because these elements more commonly form covalent bonds (Section 12.3). 

Section 12.1 Monatomic Ions with Noble-Gas Electron Configurations... 

The previous examples have involved only main-group elements since they form monatomic ions with noble gas configurations in agreement with the octet rule. This predictable behavior lets you figure out formulas of ionic products if you know the electronic configurations of the reactants. 

One factor that favors an atom of a representative element forming a monatomic ion in a compound is the formation of a stable noble gas electron configuration. Energy considerations are consistent with this observation. For example, as one mole of Li from Group LA forms one mole of Li+ ions, it absorbs 520 kj per mole of Li atoms. The IE2 value is 14 times greater, 7298 kj/mol, and is prohibitively large for the formation of Li + ions under ordinary conditions. For LE+ ions to form, an electron would have to be removed from the filled first shell. We recognize that this is unlikely. The other alkali metals behave in the same way, for similar reasons. 

The monatomic hydride and lithium ions, H and Li", duplicate the electron configuration of helium with just two electrons 15. Unlike other elements in Groups 2A/2 and 3A/13, beryllium and boron tend to form covalent bonds by sharing electrons, rather than forming ions. We will look at covalent bonds later in this chapter. Figure 12.1 is a periodic table that summarizes the elements that form monatomic ions that are isoelectronic with noble-gas atoms. 

A monatomic ion with a 2- charge has the electron configuration ls 2s 2p 3s 3/7 4s 3d °4p . (a) What neutral noble-gas atom has the same electron configuration (b) What is the monatomic ion with a 2- charge that has this configuration (c) Write the symbol of an ion with a.l+ charge that is isoelectronic with the species in (a) and (b). 

The ionic bond is the bond between charged atoms or groups of atoms (complex ions) and is the only one of the four main types of bond that can be satisfactorily described in classical (non-wave-mechanical) terms. Monatomic ions formed by elements of the earlier A subgroups and ions such as N , 0 , etc., F etc., have noble gas configurations, but many transition-metal ions and ions containing two s electrons (such as Tl and Pb " ) have less symmetrical structures. We shall not be concerned here with the numerous less stable ionic species formed in the gaseous phase. 

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