Gain, electronic

Typical elements in Groups V. VI and VII would be expected to achieve a noble gas configuration more easily by gaining electrons rather than losing them. Electron affinity is a measure of the energy change when an atom accepts an extra electron. It is difficult to measure directly and this has only been achieved in a few cases more often it is obtained from enthalpy cycle calculations (p. 74). 

Cathode is the positive electrode of a primary cell associated with chemical reactions that gain electrons from the external circuit. 

The ion detection system consists of a high-gain electron multiplier and the signal digitizing system, along with a computer for data acquisition and manipulation. 

Reduction—the reverse of oxidation a chemical change of state in which one constituent gains electrons. 

Section 1.2 An ionic bond is the force of electrostatic attraction between two oppositely charged ions. Atoms at the upper right of the periodic table, especially fluorine and oxygen, tend to gain electrons to form anions. Elements toward the left of the periodic table, especially metals such as sodium, tend to lose electrons to form cations. Ionic bonds in which carbon is the cation or anion are rare. 

VVTien two objects/particles separate after being in contact (equal charges), one par dele loses electrons and becomes positively charged while the other gains electrons and becomes negatively charged. 

Reduction occurs at the cathode, where oxygen combines with water and gains electrons to form the hydroxyl ion ... 

At each interface the interfacial potential will depend upon the chemical potentials of the species involved in the equilibrium. Thus at the Zn/Zn electrode there will be a tendency for zinc ions in the lattice to lose electrons and to pass across the interface and form hydrated ions in solution this tendency is given by the chemical potential of zinc which for pure zinc will be a constant. Similarly, there will be a tendency for hydrated Zn ions in solution to lose their hydration sheaths, to gain electrons and to enter the lattice of the metal this tendency is given by the chemical potential of the Zn ions, which is related to their activity. (See equation 20.155.) Thermodynamically... 

Active Figure 2.5 The reaction of boron trifluoride, a Lewis acid, with dimethyl ether, a Lewis base. The Lewis acid accepts a pair of electrons, and the Lewis base donates a pair of nonbonding electrons. Note how the movement of electrons from the Lewis base to the Lewis acid is indicated by a curved arrow. Note also how, in electrostatic potential maps, the boron becomes more negative (red) after reaction because it has gained electrons and the oxygen atom becomes more positive (blue) because it has donated electrons. Sign in atwww. thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

When an atom loses or gains electrons, charged particles called ions are formed. Metal atoms typically tend to lose electrons to form positively charged ions called cations (pronounced CAT-i-ons). Examples include the Na+ and Ca2+ ions, formed from atoms of the metals sodium and calcium ... 

Nonmetal atoms form negative ions (anions—pronounced AN-i-ons) by gaining electrons. Consider, for example, what happens when atoms of the nonmetals chlorine and oxygen acquire electrons ... 

This is reasonable noble-gas atoms must have an extremely stable electronic structure, because they are so unreactive. Other atoms might be expected to acquire noble-gas electronic structures by losing or gaining electrons. 

At the same time, H+ ions are reduced to H2 molecules by gaining electrons the reduction half-equation is... 

As pointed out in Chapter 2, elements close to a noble gas in the periodic table form ions that have the same number of electrons as the noble-gas atom. This means that these ions have noble-gas electron configurations. Thus the three elements preceding neon (N, O, and F) and the three elements following neon (Na, Mg, and Al) all form ions with the neon configuration, is22s22p6. The three nonmetal atoms achieve this structure by gaining electrons to form anions ... 

The ionization energy of an atom is a measure of its tendency to lose electrons the larger the ionization energy, the more difficult it is to remove an electron. There are several different ways of comparing the tendencies of different atoms to gain electrons. The most useful of these for our purposes is the dectronegativity, which measures the ability of an atom to attract to itsdf the electron pair forming a covalent bond. 

Some neutral atoms can gain electrons, forming negative ions. Thus a neutral fluorine atom can add an electron to form a negative ion, F-. This change, for fluorine atoms, does not require the input of energy it releases energy ... 

This time, copper ion gains electrons from the zinc, in contrast to the behavior in Experiment 7, where copper metal lost electrons to silver. 

We can generalize now on the use of Table 12-11. A substance on the left in Table 12-11 reacts by losing electrons. A substance on the right reacts by gaining electrons. We may draw the following conclusions ... 

As we saw in Chapter 19, chlorine represents the other extreme in chemical reactivity. Its most obvious chemical characteristic is its ability to acquire electrons to form negative chloride ions, and, in the process, to oxidize some other substance. Since the tendency to lose or gain electrons is a result of the details of the electronic structure of the atom, let us try to explain the chemistry of the third-row elements on this basis. 

An oxidising agent is one that gains electrons and is reduced a reducing agent is one that loses electrons and is oxidised. 

The periodic table can help us decide what type of ion an element forms and what charge to expect the ion to have. Fuller details will be given in Chapter 2, but we can begin to see the patterns. One major pattern is that metallic elements— those toward the left of the periodic table—typically form cations by electron loss. Nonmetallic elements—those toward the right of the table—typically form anions by gaining electrons. Thus, the alkali metals form cations, and the halogens form anions. 

The pattern of ion formation by main-group dements can be summarized by a single rule for atoms toward the left or right of the periodic table, atoms lose or gain electrons until they have the same number of electrons as the nearest noble-gas atom. Thus, magnesium loses two electrons and becomes Mg2+, which has the same number of electrons as an atom of neon. Selenium gains two electrons and becomes Se2+, which has the same number of electrons as krypton. 

We have seen that oxidation is electron loss and reduction is electron gain. Electrons are real particles and cannot just be "lost. Therefore, whenever a species is oxidized, another species must be reduced. Oxidation or reduction considered separately is like one hand clapping one transfer must occur in conjunction with the other for reaction to take place. For instance, in the reaction between chlorine and sodium bromide, the bromide ions are oxidized and the chlorine... 

Elements at the right of the p block have characteristically high electron affinities they tend to gain electrons to complete closed shells. Except for the metalloids tellurium and polonium, the members of Groups 16/VI and 17/VII are nonmetals (Fig. 1.62). They typically form molecular compounds with one another. They react with metals to form the anions in ionic compounds, and hence many of the minerals that surround us, such as limestone and granite, contain anions formed from non-metals, such as S2-, CO,2-, and S042-. Much of the metals industry is concerned with the problem of extracting metals from their combinations with nonmetals. 

All elements in the s block are reactive metals that form basic oxides. The p-block elements tend to gain electrons to complete dosed shells they range from metals through metalloids to nonmetals. 

Formulas of compounds consisting of the monatomic ions of main-group elements can be predicted by assuming that cations have lost all their valence electrons and anions have gained electrons in their valence shells until each ion has an octet of electrons, ora duplet in the case of FI, Li, and Be. 

Early experiments showed that strong electrical forces can strip electrons from atoms. Atoms can also gain electrons under the influence of electrical force. In fact, much of the chemistry that takes place in the world around us involves electrons shifting from one chemical substance to another. Chemical reactions have no effect, however, on the stmctures of nuclei. All atoms of a particular element have the same number of protons in the nucleus, and these do not change during chemical processes. The defining feature of an element, therefore, is the charge carried by the protons in its nucleus. 

By examining the changes occurring for magnesium and hydronium ions, we discover that Mg atoms lose electrons during this reaction and hydronium ions gain electrons ... 

Metallic iron is made up of neutral iron atoms held together by shared electrons (see Section 10.7). The formation of rust involves electron-transfer reactions. Iron atoms lose three electrons each, forming Fe cations. At the same time, molecular oxygen gains electrons from the metal, each molecule adding four electrons to form a pair of oxide anions. As our inset figure shows, the Fe cations combine with O anions to form insoluble F 2 O3, rust. Over time, the surface of an iron object becomes covered with flaky iron(ni) oxide and pitted from loss of iron atoms. 

Recall from Section 4- that in a redox reaction, one species loses electrons while another species gains electrons. A chemical species that loses electrons is oxidized, and a chemical species that gains electrons is reduced. 

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