Covalent bonds polyatomic ions

NH4)2S04 is an ionic solid composed of covalently bonded polyatomic ions both obey the octet rule ... 

Polar Covalent Bond Polyatomic Ions Positron Potential Energy... 

Polyatomic Ions Covalent Bonds Within Ions Many ionic compounds contain polyatomic ions, which consist of two or more atoms bonded covalently and have a net positive or negative charge. For example, the ionic compound calcium carbonate is an array of polyatomic carbonate anions and monatomic calcium cations attracted to each other. The carbonate ion consists of a carbon atom covalently bonded to three oxygen atoms, and two additional electrons give the ion its 2- charge (Figure 2.15). In many reactions, a polyatomic ion stays together as a unit. 

With the exception of Hg2 ", the ions listed in Table 3.3 are monatomic—each consists of a single atom. In polyatomic ions, two or more atoms are joined together by covalent bonds. These ions are common, especially among the nonmetals. A number of polyatomic ions and compounds containing them are listed in Table 3.5. From this table, you can see the following ... 

The ions dealt with to this point (e.g., Na+, Cl-) are monatomic that is, they are derived from a single atom by the loss or gain of electrons. Many of the most important ions in chemistry are polyatomic, containing more than one atom. Examples include the hydroxide ion (OH-) and the ammonium ion (NH ). In these and other polyatomic ions, the atoms are held together by covalent bonds, for example,... 

This chapter is devoted to the covalent bond as it exists in molecules and polyatomic ions. We consider—... 

These examples illustrate the principle that atoms in covalently bonded species tend to have noble-gas electronic structures. This generalization is often referred to as the octet rule. Nonmetals, except for hydrogen, achieve a noble-gas structure by sharing in an octet of electrons (eight). Hydrogen atoms, in molecules or polyatomic ions, are surrounded by a duet of electrons (two). 

In the polyatomic ion the formation of a coordinate covalent bond between nitrogen and hydrogen involves —... 

Distinguish between each of the following pairs (a) an ion and an ionic bond, (b) an ion and a free atom, (c) a covalent bond and an ionic bond, (cl) a triple bond and three single bonds on the same atom, (e) a polyatomic molecule and a polyatomic ion. 

The constituent atoms in polyatomic ions are also linked by covalent bonds. In these cases, the net charge on the ion is determined by the total number of electrons and the total number of protons. For example, the ammonium ion, NH4 +, formed from five atoms, contains one fewer electron than the number of protons. A nitrogen atom plus 4 hydrogen atoms contains a total of 11 protons and 11 electrons, but the ion has only 10 electrons, 8 of which are valence electrons. 

Polyatomic ions, such as OH , NO,, and NH4 + possess covalent bonds as well as an overall charge. 

The charges on polyatomic ions cause ionic bonding between these groups of atoms and oppositely charged ions. In writing electron dot structures, the distinction between ionic and covalent bonds must be clearly indicated. For example, an electron dot diagram for the compound NH4NO, would be... 

Ionic bonding results from electrostatic interactions between ions, which can be formed by the transfer of one or more electrons from a metal to a nonmetal or group of nonmetals (forming a polyatomic ion, like N03 ). Covalent bonding, on the other hand, results from sharing one or more electron pairs between two nonmetal atoms. 

Ionic compounds are made up of positively charged ions (usually metal ions) and negatively charged ions (usually non-metal ions or polyatomic anions) held together by electrostatic forces of attraction. Molecular compounds are made up of discrete units called molecules. Generally they consist of a small number of nonmetal atoms held together by covalent bonds (sharing of electrons). 

Force Within Unit (Intra) covalent bond within polyatomic ion — — covalent bond... 

Some ionic compounds contain a combination of bonds. For instance, in polyatomic ions such as ammonium (NH4+), the hydrogen atoms are bonded to the nitrogen atom by polar covalent bonds. The ionic bond is thus between this covalently bonded moiety and another oppositely charged ion such as chloride (CT). 

In Sections 9-3 and 9-4, we will show you two types of chemical bonds ionic and covalent. It is important to be able to represent compounds in terms of the atoms and valence electrons that make up the chemical species (compounds or polyatomic ions). One of the best ways is to use Lewis symbols and structures. 

You know that a covalent bond involves the sharing of a pair of electrons between two atoms each atom contributes one electron to the shared pair. In some cases, such as the hydronium ion, HsO", one atom contributes both of the electrons to the shared pair. The bond in these cases is called a co-ordinate covalent bond. In terms of the quantum mechanical model, a co-ordinate covalent bond forms when a filled atomic orbital overlaps with an empty atomic orbital. Once a co-ordinate bond is formed, it behaves in the same way as any other single covalent bond. The next Sample Problem involves a polyatomic ion with a co-ordinate covalent bond. 

Oxidation numbers are just a bookkeeping method used to keep track of electron transfers. In a covalent molecule or a polyatomic ion, the oxidation number of each element does not represent an ionic charge, because the elements are not present as ions. However, to assign oxidation numbers to the elements in a covalent molecule or polyatomic ion, you can pretendthe bonds are ionic. 

Force within units Covalent bond within polyatomic ion Atomic forces between subatomic particles Atomic forces between subatomic particles Covalent bond... 

Sorry, it s true. Not only are polyatomic ions annoying because you have to memorize them, but they pop up everywhere. If you don t memorize the polyatomic ions, you ll waste time trying to figure out weird (and incorrect) covalent bonding cirrangements when what you re really dealing with is a straightforwcird ionic compound. Here are the common polyatomic ions in Table 22-1 (see Chapter 6 for more information on these ions). 

Polyatomic ions, such as the ammonium ion, NH4+, or the sulfate ion, S042-, consist of atoms held together with covalent bonds. We use... 

Almost simultaneous with the publication of Kossel s paper there appeared a rival electronic theory. The American chemist Lewis introduced the idea of the covalent electron-pair bond. Like Kossel, he was impressed by the apparent stability of the noble gas configuration. He was also impressed by the fact that, apart from many compounds of the transition elements, most compounds when rendered as molecules have even numbers of electrons, suggesting that electrons are usually found in pairs. Lewis devised the familiar representations of molecules and polyatomic ions (Lewis structures, or Lewis diagrams) in which electrons are shown as dots (or as noughts and crosses) to show how atoms can attain noble gas configurations by the sharing of electrons in pairs, as opposed to complete transfer as in Kossel s theory. It was soon apparent from the earliest X-ray studies that Kossel s theory was more appropriate... 

This section attempts a systematic classification of the covalent bonding schemes, in terms of VB theory, exhibited by atoms of the Main Group elements. The aim is to enable the reader to fit together the structure of a molecule or polyatomic ion by identifying the appropriate bonding scheme for each atom. You should try not to memorise by rote the tables in this section the material should be studied in conjunction with a text which covers the descriptive chemistry in some detail. The lists of bonding schemes are not exhaustive, but they contain the most important ones. 

These structures are shown in Figure 8-1, where the shared electron pair is represented by a line between the bonded atoms. Polyatomic ions like NHJ and OH- also have structures obeying the octet rule. Notice that in the structures of Figure 8-1, H has a share of two electrons, which is as expected if it is to attain the He configuration we might say that H obeys the doublet rule. Similar reasoning applied to covalently bonded transition metals allows an expansion beyond eight electrons. 

The first reaction is much faster than the second. As Mn04 ion is common in both the reactions, the difference clearly lies in the nature of ferrous and oxalate ions. Fe2+ ion is a simple ion, whereas C2042- ion is a polyatomic ion and contains a number of covalent bonds which have to be broken in the oxidation reaction. 

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