Nonmetals electron gain

To predict the electron configuration of a monatomic cation, remove outermost electrons in the order np, ns, and (n — l)d fora monatomic anion, add electrons until the next noble-gas configuration has been reached. The transfer of electrons results in the formation of an octet (or duplet) of electrons in the valence shell on each of the atoms metals achieve an octet (or duplet) by electron loss and nonmetals achieve it by electron gain. 

B) Metals have ionization energies (or ionization potentials) that are much lower than those of the nonmetals since a smaller amount of energy is required to remove an electron from a metal than from a nonmetal. Removal of an electron(s) is called oxidation. Nomnetals, on the other hand, have high electron affinities compared to metals and tend to gain electrons. Gain of electrons is called reduction. 

Now we can work out the formula of an ionic compound formed between the monatomic ions of two main-group elements, one a metal and the other a nonmetal. Unless a lower oxidation number is specified (as for the p-block metals), the metal atom loses all its valence electrons, and the nonmetal atom gains enough electrons to complete its valence shell. Then we adjust the numbers of cations and anions so that the resulting compound is electrically neutral. A simple example is calcium chloride. The calcium atoms ([Ar]4s2) each lose two electrons, to form... 

We saw in the last chapter that the bond formed between a metal and a reactive nonmetal typically involves the transfer of electrons. The metal atom loses one or more electrons and becomes a cation, while the reactive nonmetal atom gains one or more electrons and becomes an anion. The oppositely charged ions are held together by the electrostatic attractions that we call ionic bonds. 

There are general reactivity trends on the periodic table that are useful to know. Metals and nonmetals usually combine to form ionic compounds with the metal giving up an electron to become positively charged and the nonmetal element gaining an electron to become... 

If the reactants in an equation are two elements, the only way in which they can react is to form a binary compound, which is composed of two elements. Often, when a metal reacts with a nonmetal, electrons are transferred and an ionic compound is formed. You can use the charges of the ions to predict the formula of the compound formed. Metals in Groups I and 2 lose one electron and two electrons, respectively. Nonmetals in Groups 16 and 17 gain two electrons and one electron, respectively. Using the charges on the ions, you can predict the formula of the product of a synthesis reaction, such as the one in Figure 10. 

Because hydrogen has a single electron, it can behave as a metal and lose an electron or behave as a nonmetal and gain an electron. 

The ratio of ions must be such that the number of electrons lost by the metal is equal to the number of electrons gained by the nonmetal. Because the sum of the oxidation numbers of these ions is zero, these ions must be present in a one-to-one ratio. One sodium ion transfers one electron to one chloride ion, and the formula unit is NaCl. 

Ionize (anion) Attach electron(s) to the gaseous nonmetal atom to form the gaseous anion. Several electron affinity values may be required. Recall that for electron gain, A//= - ea for each electron added. 

Ionic bonds form when a metal atom loses one or more electrons and a nonmetal atom gains one or more electrons. 

Elements with high electronegativities (nonmetals) often gain electrons to form anions. Elements with low electronegativities (metals) often lose electrons to form cations. 

Group VIIA nonmetals must gain one electron to form anions with noble gas configurations. 

Figure 9.4 Lewis electron-dot symbols for elements in Periods 2 and 3. The element symbol represents the nucleus and Inner electrons, and the dots around It represent valence electrons, either paired or unpaired. The number of unpaired dots Indicates the number of electrons a metal atom loses, or the number a nonmetal atom gains, or the number of covalent bonds a nonmetal atom usually forms.

Nonmetal ions As shown in Table 7.3, nonmetals gain the number of electrons that, when added to their valence electrons, equals 8. For example, consider phosphorus, with five valence electrons. To form a stable octet, the atom gains three electrons and forms a phosphide ion with a 3- charge. Likewise, oxygen, with six valence electrons, gains two electrons and forms a oxide ion with a 2- charge. 

Nonmetal atoms gain electrons from metals to form negative ions. The smaller the nonmetal atom, the higher the reactivity of the nonmetal. For example, fluorine atoms are the smallest of Group 7A elements, and fluorine is the most reactive nonmetal. It reacts with all other elements except three... 

The reaction of Cu with Og can be recognized as a redox reaction because it is the addition of oxygen to a reactant and also because it is the combination of a metal and a nonmetal. Since the product is an ionic compound, the electron gain and loss is determined by the charges on the ions. The oxide CuO must be composed of Cu " and ions. Therefore, the copper metal has been oxidized by the loss of two electrons from each atom, and the oxygen has been reduced by the gain of two electrons by each atom. 

It is the chemical properties of metals and nonmetals that interest us most. Metals tend to lose electrons and form positive ions, while nonmetals tend to gain electrons and form negative ions. When a metal reacts with a nonmetal, electrons are often transferred from the metal to the nonmetal. 

We can apply this principle in predicting the formulas of ionic compounds. To predict the formula of an ionic compound, we must recognize that chemical compounds are always electrically neutral. In addition, the metal will lose electrons to achieve noble gas configuration and the nonmetal will gain electrons to achieve noble gas configuration. Consider the compound formed between barium and sulfur. Barium has two valence electrons, whereas sulfur has six valence electrons ... 

Elements with high electronegativities (nonmetals) often gain electrons to form anions. 

Ionic compounds form when a metal transfers electrons to a nonmetal, and the resulting positive and negative ions attract each other to form a three-dimensional array. In many cases, metal atoms lose and nonmetal atoms gain enough electrons to attain the same number of electrons as in atoms of the nearest noble gas. Covalent compounds form when elements, usually nonmetals, share electrons. Each covalent bond is an electron pair mutually attracted by two atomic nuclei. Monatomic ions are derived from single atoms. Polyatomic ions consist of two or more covalently bonded atoms that have a net positive or negative charge due to a deficit or excess of electrons. 

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