Sodium oxidation numbers

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the state(s) of oxidation, eg, titanium(II) chloride for TiCl2, iron(II) oxide for FeO, titanium(III) chloride for TiCl, iron(III) oxide for Fe203, titanium(IV) chloride for TiCl, and iron(II,III) oxide for Fe O. In this system, only the termination -ate is used for anions, followed by Roman numerals in parentheses. Examples are potassium manganate(IV) for K2Mn02, potassium tetrachloroplatinate(II) for K PtCl, and sodium hexacyanoferrate(III) for Na3Fe(CN)3. Thus a set of prefixes and terminations becomes uimecessary. 

The oxidation-number system is easily extended to include other coordination compounds. Even the interesting substances represented by the formulas Na4Ni(CN)4 and K4Pd(CN)4 create no nomenclature problem they become sodium tetracyanonickelate(0) and potassium tetracyanopaHadate(0), respectively. 

The oxidation number of an element in a monatomic ion is equal to the charge of that ion. In the ionic compound NaCl, sodium has an oxidation number of +1, chlorine an oxidation number of — 1. The oxidation numbers of aluminum and oxygen in A1203 (Al3+, O2- ions) are +3 and —2, respectively. 

What is the oxidation number of phosphorus in sodium phosphite, Na3P03 In the dihydrogen phosphate ion ... 

The name of a monatomic cation is the same as the name of the element forming it, with the addition of the word ion, as in sodium ion for Na+. When an element can form more than one kind of cation, such as Cu+ and Cu2+ from copper, we use the oxidation number, the charge of the cation, written as a Roman numeral in parentheses following the name of the element. Thus, Cu+ is a copper(I) ion and Cu2+ is a copper(II) ion. Similarly, Fe2+ is an iron(II) ion and Fe3" is an iron(III) ion. As shown in Fig. C.6, most transition metals form more than one kind of ion so unless we are given other information we need to include the oxidation number in the names of their compounds. 

Write a balanced chemical equation for (a) the reaction between sodium hydride and water (b) the formation of synthesis gas (c) the hydrogenation of ethene, H,C= GH2, and give the oxidation number of the carbon atoms in the reactant and product (d) the reaction of magnesium with hydrochloric acid. 

The principal use of sodium chlorate is as a source of chlorine dioxide, C102. The chlorine in C102 has oxidation number +4, and so the chlorate must be reduced to form it. Sulfur dioxide is a convenient reducing agent for this reaction ... 

Perchloric acid, HC104, is prepared by the action of concentrated hydrochloric acid on sodium perchlorate, followed by distillation. It is a colorless liquid and the strongest of all common acids. Because chlorine has its highest oxidation number, +7, in these compounds, they are powerful oxidizing agents contact between perchloric acid and even a small amount of organic material can result in a dangerous explosion. 

Identify the oxidation number of the halogen atoms in (a) iodine heptafluoride (b) sodium periodate (c) hypobromous acid (d) sodium chlorite. 

The composition of sodium polysulfide solutions saturated with sulfur of zero oxidation number (S°) has also been studied at 25 and 80 °C (solutions in contact with elemental sulfur) [76]. In this case the ratio 8° 8 per polysulfide ion increases with increasing alkahnity. The maximum average number of sulfur atoms per polysulfide molecule was obtained as 5.4 at 25 °C and 6.0 at 80 °C and pH values of >12. Equilibrium constants for reactions as in Eqs. (26) and (27) have been derived assuming various models with differing numbers of polysulfide ions present. 

NaOCl Sodium hypochlorite is ionic, containing Na cations and OCl anions. The sodium cation has oxidation number equal to its charge, +1. In the anion, oxygen is -2 (Guideline 4), so chlorine must be +1 for the sum of the oxidation numbers to match the -1 charge of the hypochlorite anion (Guideline 2). 

Naming of the positive ion depends on whether the cation is monatomic (has one atom). If not, the special names given in Sec. 6.3.2 are used. If the cation is monatomic, the name depends on whether the element forms more than one positive ion in its compounds. For example, sodium forms only one positive ion in all its compounds—NaT Iron forms two positive ions—Fc2r and Fe,+. Cations of elements that form only one type of ion in all their compounds need not be further identified in the name. Thus, Na may simply be called the sodium ion. Cations of metals that occur with two or more different charges must be further identified. Fe(NO,)2 and Fe(NO,)3 occur with Fc2+ and Fe3 ions, respectively. If we just call the ion the iron ion, we will not know which one it is. Therefore, for monatomic cations, we use a Roman numeral in parentheses attached to the name to tell the charge on such ion. (Actually, oxidation numbers are used for this purpose, but if you have... 

EXAMPLE 13.4. Calculate the oxidation number of N in NaN, sodium azide. 

EXAMPLE 13.6. Give the possible oxidation numbers for sodium. 

It may appear strange that the term reduction is associated with a gaining process. Actually, the term reduction was coined as a result of what happens to the oxidation number of the element when the electron transfer takes place. The oxidation number of an element is a number representing the state of the element with respect to the number of electrons the element has given up, taken on, or contributed to a covalent bond. For example, pure sodium metal has neither given up, taken on, nor shared electrons, and thus its oxidation number is zero. In sodium chloride, however, the sodium has given up an electron and becomes a +1 charge thus its oxidation number is +1. The chlorine in NaCl has taken on an electron... 

When finding the oxidation numbers of elements in ionic compounds, you can work with the ions separately. For example, Na2Cr207 contains two Na" ions, and so sodium has an oxidation number of+1. The oxidation numbers of Cr and 0 can then be calculated as shown in part (c) of the Sample Problem. 

A single-atom ion is assigned an oxidation number equal to its electrical charge. Examples are sodium or iron ions, the latter occurring in two oxidation states ... 

The second of Faradays laws states that a given quantity of electricity produces fewer moles of substances with higher oxidation numbers. Compare the reduction of sodium and calcium ions ... 

The oxidations take place without affecting the sulfur atom when it is in one of its highest oxidation states (i.e., sulfur has an oxidation number of the value + 4 or +6, see Table 18). Thus, epoxidation of (pcntafluorosulfanyl)alkenes, e. g. 1, is achieved by treatment with sodium hypochlorite under phase transfer catalytic conditions.281... 

Halides of metals tend to be ionic unless the metal has an oxidation number greater than +2. For example, sodium chloride and copper(II) chloride are ionic compounds and have high melting points, but TiCl4 and FeCl3 sublime as molecules. 

The key to the oxidation-number method of balancing redox equations is to realize that the net change in the total of all oxidation numbers must be zero. That is, any increase in oxidation number for the oxidized atoms must be matched by a corresponding decrease in oxidation number for the reduced atoms. Take the reaction of potassium permanganate (KMn04) with sodium bromide in aqueous acid, for example. An aqueous acidic solution of the purple permanganate anion (Mn04 ) is reduced by Br- to yield the nearly colorless Mn2+ ion, while Br- is oxidized to Br2. The unbalanced net ionic equation for the process is... 

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