{"id":2036,"date":"2023-10-02T08:38:02","date_gmt":"2023-10-02T08:38:02","guid":{"rendered":"http:\/\/localhost\/ecole9ja\/?p=2036"},"modified":"2023-10-02T08:43:01","modified_gmt":"2023-10-02T08:43:01","slug":"week-7-ss1-first-term-chemistry-notes-2","status":"publish","type":"post","link":"https:\/\/ecolebooks.com\/nigeria\/posts\/week-7-ss1-first-term-chemistry-notes-2\/","title":{"rendered":"Week 7 – SS1 First Term Chemistry Notes"},"content":{"rendered":"

WEEK 7
\n<\/strong>COMPOUND
\n<\/strong>In chemistry, a compound is a substance that results from a combination of two or more different chemical element s, in such a way that the atom s of the different elements are held together by chemical bonds that are difficult to break. These bonds form as a result of the sharing or exchange of electron s among the atoms. The smallest unbreakable unit of a compound is called a molecule<\/p>\n

Examples of compounds:\u00a0\u00a0\u00a0\u00a0
\n<\/h3>\n
    \n
  • \n
    water (H2<\/sub>O)\n<\/div>\n<\/li>\n
  • \n
    table salt (NaCl)\n<\/div>\n<\/li>\n
  • \n
    sucrose (table sugar, C12<\/sub>H22<\/sub>O11<\/sub>\n\t\t\t\t<\/div>\n<\/li>\n<\/ul>\n

    The relationship is simple.\u00a0
    \nAtoms are what all matter are ultimately made up of.\u00a0 Atoms are the smallest units of an element.\u00a0
    \nElements are substances composed of all the same type of atoms, and have specific chemical properties.\u00a0 Aluminum for example contains only Aluminum atoms, and no other, and has chemical properties specific to Aluminum.
    \nMolecules are combinations of atoms that are not necessarily all the same element.\u00a0 Sometimes they are the same element, like air molecules.\u00a0 Air molecules are a mix of pairs of Nitrogen, and pairs of Oxygen.\u00a0 Although the pairs of atoms are the same element, they are more than one atom so they are molecules.\u00a0 Water molecules are made of Hydrogen atoms and Oxygen atoms, i.e. different elements.\u00a0
    \nCompounds are combinations of elements into new substances, like water.\u00a0 Water combines the elements of Hydrogen and Oxygen and has chemical properties distinct from the elements it’s made of.\u00a0<\/p>\n

    \u00a0Long before chemists knew the formulas for chemical compounds, they developed a system of nomenclature<\/strong> that gave each compound a unique name. Today we often use chemical formulas, such as NaCl, C12<\/sub>H22<\/sub>O11<\/sub>, and Co(NH3<\/sub>)6<\/sub>(ClO4<\/sub>)3<\/sub>, to describe chemical compounds. But we still need unique names that unambiguously identify each compound.<\/p>\n

    \u00a0Common Names <\/em><\/strong>
    \n\t\tSome compounds have been known for so long that a systematic nomenclature cannot compete with well-established common names. Examples of compounds for which common names are used include water (H2<\/sub>O), ammonia (NH3<\/sub>), and methane (CH4<\/sub>).<\/p>\n

    \u00a0
    \n\u00a0Naming Ionic Compounds <\/em><\/strong>
    \n\t\t(Metals with Non-metals)
    \nThe names of ionic compounds are written by listing the name of the positive ion followed by the name of the negative ion.
    \nNaCl\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0sodium chloride
    \n(NH4<\/sub>)2<\/sub>SO4<\/sub>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ammonium sulfate
    \nNaHCO3<\/sub>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0sodium bicarbonate
    \nWe therefore need a series of rules that allow us to unambiguously name positive and negative ions before we can name the salts these ions form.<\/p>\n

    \u00a0
    \n\u00a0Naming Positive Ions<\/em><\/strong>
    \n\t\tMonatomic positive ions have the name of the element from which they are formed.
    \nNa+<\/sup>\u00a0\u00a0\u00a0\u00a0sodium \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Zn2+<\/sup>\u00a0\u00a0\u00a0\u00a0zinc
    \nCa2+<\/sup>\u00a0\u00a0\u00a0\u00a0calcium \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H+<\/sup>\u00a0\u00a0\u00a0\u00a0hydrogen
    \nK+<\/sup>\u00a0\u00a0\u00a0\u00a0potassium \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Sr2+<\/sup>\u00a0\u00a0\u00a0\u00a0strontium
    \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
    \nSome metals form positive ions in more than one oxidation state. One of the earliest methods of distinguishing between these ions used the suffixes -ous<\/em> and -ic<\/em> added to the Latin name of the element to represent the lower and higher oxidation states, respectively.
    \nFe2+<\/sup>\u00a0\u00a0\u00a0\u00a0ferrous \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Fe3+<\/sup>\u00a0\u00a0\u00a0\u00a0ferric
    \nSn2+<\/sup>\u00a0\u00a0\u00a0\u00a0stannous \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Sn4+<\/sup>\u00a0\u00a0\u00a0\u00a0stannic
    \nCu+<\/sup>\u00a0\u00a0\u00a0\u00a0cuprous \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Cu2+<\/sup>\u00a0\u00a0\u00a0\u00a0cupric
    \nChemists now use a simpler method, in which the charge on the ion is indicated by a Roman numeral in parentheses immediately after the name of the element.
    \nFe2+<\/sup>\u00a0\u00a0\u00a0\u00a0iron(II) \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Fe3+<\/sup>\u00a0\u00a0\u00a0\u00a0iron (III)
    \nSn2+<\/sup>\u00a0\u00a0\u00a0\u00a0tin(II) \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Sn4+<\/sup>\u00a0\u00a0\u00a0\u00a0tin(IV)
    \nCu+<\/sup>\u00a0\u00a0\u00a0\u00a0copper(I) \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Cu2+<\/sup>\u00a0\u00a0\u00a0\u00a0copper(II)
    \nPolyatomic positive ions often have common names ending with the suffix -onium<\/em>.
    \nH3<\/sub>O+<\/sup>\u00a0\u00a0\u00a0\u00a0hydronium
    \nNH4<\/sub>+<\/sup>\u00a0\u00a0\u00a0\u00a0ammonium <\/p>\n

    \u00a0
    \n\u00a0Naming Negative Ions<\/em><\/strong>
    \n\t\tNegative ions that consist of a single atom are named by adding the suffix -ide<\/em> to the stem of the name of the element.
    \nF–<\/sup>\u00a0\u00a0\u00a0\u00a0fluoride \u00a0\u00a0\u00a0\u00a0O2-<\/sup>\u00a0\u00a0\u00a0\u00a0oxide
    \nCl–<\/sup>\u00a0\u00a0\u00a0\u00a0chloride \u00a0\u00a0\u00a0\u00a0S2-<\/sup>\u00a0\u00a0\u00a0\u00a0sulfide
    \nBr–<\/sup>\u00a0\u00a0\u00a0\u00a0bromide \u00a0\u00a0\u00a0\u00a0N3-<\/sup>\u00a0\u00a0\u00a0\u00a0nitride
    \nI–<\/sup>\u00a0\u00a0\u00a0\u00a0iodide \u00a0\u00a0\u00a0\u00a0P3-<\/sup>\u00a0\u00a0\u00a0\u00a0phosphide
    \nH–<\/sup>\u00a0\u00a0\u00a0\u00a0hydride\u00a0\u00a0\u00a0\u00a0C4-<\/sup>\u00a0\u00a0\u00a0\u00a0carbide
    \n\t\t\u00a0
    \n\u00a0Common Polyatomic Negative Ions<\/em><\/strong>
    \n\t\t\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0-1 ions<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
    \nHCO3<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0bicarbonate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HSO4<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0hydrogen sulfate (bisulfate)
    \nCH3<\/sub>CO2<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0acetate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ClO4<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0perchlorate
    \nNO3<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0nitrate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ClO3<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0chlorate
    \nNO2<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0nitrite \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ClO2<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0chlorite
    \nMnO4<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0permanganate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ClO–<\/sup>\u00a0\u00a0\u00a0\u00a0hypochlorite
    \nCN–<\/sup>\u00a0\u00a0\u00a0\u00a0cyanide\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0OH–<\/sup>\u00a0\u00a0\u00a0\u00a0hydroxide
    \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0-2 ions<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
    \nCO3<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0carbonate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0O2<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0peroxide
    \nSO4<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0sulfate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0CrO4<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0chromate
    \nSO3<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0sulfite\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Cr2<\/sub>O7<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0dichromate
    \nS2<\/sub>O3<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0thiosulfate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HPO4<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0hydrogen phosphate
    \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0-3 ions<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
    \nPO4<\/sub>3-<\/sup>\u00a0\u00a0\u00a0\u00a0phosphate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0AsO4<\/sub>3-<\/sup>\u00a0\u00a0\u00a0\u00a0arsenate
    \nBO3<\/sub>3-<\/sup>\u00a0\u00a0\u00a0\u00a0borate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/p>\n

    \u00a0
    \n\u00a0Naming Polyatomic Ions<\/strong>
    \n\t\tAt first glance, the nomenclature of the polyatomic negative ions in the table above seems hopeless. There are several general rules, however, that can bring some order out of this apparent chaos.
    \nThe name of the ion usually ends in either -ite<\/em> or -ate<\/em>. The -ite<\/em> ending indicates a low oxidation state. Thus,the NO2<\/sub>–<\/sup> ion is the nitrite ion.
    \nThe -ate<\/em> ending indicates a high oxidation state. The NO3<\/sub>–<\/sup> ion, for example, is the nitrate ion.
    \nThe prefix hypo<\/em>– is used to indicate the very lowest oxidation state. The ClO- ion, for example, is the hypochlorite ion.
    \nThe prefix per<\/em>– (as in hyper-) is used to indicate the very highest oxidation state. The ClO4<\/sub>–<\/sup> ion is therefore the perchlorate ion.
    \nThere are only a handful of exceptions to these generalizations. The names of the hydroxide (OH–<\/sup>), cyanide (CN–<\/sup>), and peroxide (O2<\/sub>2-<\/sup>) ions, for example, have the -ide<\/em> ending because they were once thought to be monatomic ions.
    \nNaming Simple Covalent Compounds<\/em><\/strong>
    \n\t\t( Non-metals with non-metals )
    \nOxidation states also play an important role in naming simple covalent compounds. The name of the atom in the positive oxidation state is listed first. The suffix -ide<\/em> is then added to the stem of the name of the atom in the negative oxidation state.
    \nHCl\u00a0\u00a0\u00a0\u00a0hydrogen chloride
    \nNO \u00a0\u00a0\u00a0\u00a0nitrogen oxide
    \nBrCl\u00a0\u00a0\u00a0\u00a0bromine chloride
    \nAs a rule, chemists write formulas in which the element in the positive oxidation state is written first, followed by the element(s) with negative oxidation numbers.
    \nThe number of atoms of an element in simple covalent compounds is indicated by adding one of the following Greek prefixes to the name of the element.
    \n1 mono-\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a06 hexa-
    \n2 di-\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a07 hepta-
    \n3 tri- \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a08 octa-
    \n4 tetra- \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a09 nona-
    \n5 penta- \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a010 deca-
    \nThe prefix mono<\/em>– is seldom used because it is redundant. The principal exception to this rule is carbon monoxide (CO).<\/p>\n

    \u00a0
    \n\u00a0Naming Acids<\/em><\/strong>
    \n\t\tSimple covalent compounds that contain hydrogen, such as HCl, HBr, and HCN, often dissolve in water to produce acids. These solutions are named by adding the prefix hydro<\/em>– to the name of the compound and then replacing the suffix -ide<\/em> with -ic<\/em>. For example, hydrogen chloride (HCl) dissolves in water to form hydrochloric acid; hydrogen bromide (HBr) forms hydrobromic acid; and hydrogen cyanide (HCN) forms hydrocyanic acid.
    \nMany of the oxygen-rich polyatomic negative ions in Table 2.1 form acids that are named by replacing the suffix –ate<\/em> with -ic<\/em> and the suffix -ite<\/em> with -ous<\/em>.
    \nAcids containing ions ending with ide<\/em><\/strong> often become \u00a0\u00a0\u00a0\u00a0hydro -ic acid<\/em><\/strong>
    \n\t\tCl–<\/sup>\u00a0\u00a0\u00a0\u00a0chloride\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HCl\u00a0\u00a0\u00a0\u00a0hydrochloric acid
    \nF–<\/sup>\u00a0\u00a0\u00a0\u00a0fluoride\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HF \u00a0\u00a0\u00a0\u00a0hydrofluoric acid
    \nS2-<\/sup>\u00a0\u00a0\u00a0\u00a0sulfide\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H2<\/sub>S \u00a0\u00a0\u00a0\u00a0hydrosulfuric acid
    \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
    \nAcids containing ions ending with ate<\/em><\/strong> usually become \u00a0\u00a0\u00a0\u00a0-ic acid<\/em><\/strong>
    \n\t\tCH3<\/sub>CO2–<\/sup>\u00a0\u00a0\u00a0\u00a0acetate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0CH3<\/sub>CO2<\/sub>H \u00a0\u00a0\u00a0\u00a0acetic acid
    \nCO3<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0carbonate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H2<\/sub>CO3<\/sub>\u00a0\u00a0\u00a0\u00a0carbonic acid
    \nBO3<\/sub>3-<\/sup>\u00a0\u00a0\u00a0\u00a0borate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H3<\/sub>BO3<\/sub>\u00a0\u00a0\u00a0\u00a0boric acid
    \nNO3<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0nitrate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HNO3<\/sub>\u00a0\u00a0\u00a0\u00a0nitric acid
    \nSO4<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0sulfate\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H2<\/sub>SO4<\/sub>\u00a0\u00a0\u00a0\u00a0sulfuric acid
    \nClO4<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0perchlorate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HClO4<\/sub>\u00a0\u00a0\u00a0\u00a0perchloric acid
    \nPO4<\/sub>3-<\/sup>\u00a0\u00a0\u00a0\u00a0phosphate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H3<\/sub>PO4<\/sub>\u00a0\u00a0\u00a0\u00a0phosphoric acid
    \nMnO4<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0permanganate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HMnO4<\/sub>\u00a0\u00a0\u00a0\u00a0permanganic acid
    \nCrO4<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0chromate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H2<\/sub>CrO4<\/sub>\u00a0\u00a0\u00a0\u00a0chromic acid
    \nClO3<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0chlorate \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HClO3<\/sub>\u00a0\u00a0\u00a0\u00a0chloric acid
    \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
    \nAcids containing ions ending with ite<\/em><\/strong> usually become \u00a0\u00a0\u00a0\u00a0-ous acid<\/em><\/strong>
    \n\t\tClO2<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0chlorite \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HClO2<\/sub>\u00a0\u00a0\u00a0\u00a0chlorous acid
    \nNO2<\/sub>–<\/sup>\u00a0\u00a0\u00a0\u00a0nitrite \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HNO2<\/sub>\u00a0\u00a0\u00a0\u00a0nitrous acid
    \nSO3<\/sub>2-<\/sup>\u00a0\u00a0\u00a0\u00a0sulfite\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0H2<\/sub>SO 3<\/sub>\u00a0\u00a0\u00a0\u00a0sulfurous acid
    \nClO–<\/sup>\u00a0\u00a0\u00a0\u00a0hypochlorite \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0HClO\u00a0\u00a0\u00a0\u00a0hypochlorous acid
    \nComplex acids can be named by indicating the presence of an acidic hydrogen as follows.
    \nNaHCO3<\/sub>\u00a0\u00a0\u00a0\u00a0sodium hydrogen carbonate (also known as sodium bicarbonate)
    \nNaHSO3<\/sub>\u00a0\u00a0\u00a0\u00a0sodium hydrogen sulfite (also known as sodium bisulfite)
    \nKH2<\/sub>PO4<\/sub>\u00a0\u00a0\u00a0\u00a0potassium dihydrogen phosphate
    \nValency
    \nThe valency of an atom is the number of single chemical bonds that it can make (in the case of a covalently bonding substance) or the number of electrical charges that it carries (for an ion). Notice that once again the nature of the substance in question requires that the definitions be adapted appropriately. The concept of valence can be used to find the formula of a compound from the valencies of its constituent elements, or to find the valency of an elements within a compound of known formula.
    \nEvery atom within a substance is assigned a valency number that is either positive or negative. The total sum of all of the valencies within a formula unit is zero
    \nUsing valencies
    \nOnce the valencies of a few elements are known it becomes a simple matter to construct the formula of unknown compounds using the valency method. Remember that the sum of the valencies of all of the atoms in the compound must equal zero.
    \nWhere an atom may have either positive or negative valency, it is negative if it is the more electronegative element in the compound and positive if not.
    \nExample: From the water molecule above we know that the valency of hydrogen is +1.
    \nIf the valency of nitrogen in ammonia is -3 then we can construct the formula of ammonia thus:
    \nWe need enough hydrogens to cancel out the -3 valency of nitrogen. Each hydrogen = +1 therefore we need three hydrogen atoms.
    \nThe formula of ammonia = NH3<\/sub><\/strong>
    \n\t\t\"\"\/
    \n\t\t\"\"top
    \nWorking with ions
    \nWhen using valencies to work out the formula of an ion we have to remember the final charge on the ion must equal the sum of the valencies, taking into account whether the valency of each atom is negative or positive.
    \nExample: Find the formula of the sulfate (2-) ion given that the valency of the sulfur atom is +VI and the valency of the oxygen atom is -II
    \nOxygen always has negative valencies (unless bonded to fluorine)
    \nThere is one sulfur atom with a valency of +6 and overall the ion has a valency of -2
    \nTherefore +6 +(xO) = -2
    \nTherefore (xO) = -2 -6 = -8
    \neach O =-2 therfore there are four oxgen atoms in the ion
    \nFormula of the sulfate ion = SO4<\/sub>2-<\/sup><\/strong>
    \n\t\tEVALUATION
    \n1.write the symbols and the valencies of the following:
    \ni. Iron ii. potassium iii. Oxygen iv. Chlorine
    \n2. What is valency?<\/p>\n

    \t\t\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

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