Ligands and Complex Ions Chemistry Tutorial There is a bit of unique nomenclature to complex ions: The metal is known as the central metal ion.The anions or molecules attached to the metal are called ligands. Coordination Compounds Notes | Chapter 9 | Chemistry | CBSE Colors of Transition Metal Complexes | Transition Metals Zinc compounds, like those of main group elements, are mostly colourless.Exceptions occur when the compound contains a coloured anion or ligand.However, zinc selenide and zinc telluride are both coloured due to charge-transfer processes. (b) Similarly, in the complex [Ni (NH3)4]Cl2, the coordination number of the central atom (Ni) is 4. Find the oxidation number of S in SO4^2 - ion? bis(ethylenediamine) is used to indicate two ethylenediamine ligands. e.g., [CU(CN 4) 3-, oxidation number of copper is +1, and represented as Cu(I). PDF Naming Coordination Compounds Prefixes (see Rule #4 below) that give the number of ligands are NOT considered part of the ligand name in determining alphabetical order. While fully ionic bonds are not found in nature, many bonds exhibit strong ionicity, making . oxidation number of ligands list - Engage Headlines Ligands and chelates. Naming of ligands: The ligands may be negative , neutral or positive. complex ions - names Note that the number of anionic ligands . The coordination number of the central metal atom/ion may be used to deduce the molecular geometry of the coordination compound. Don't forget that the two different ligands are named in alphabetical order - aqua before hydroxo - ignoring the prefixes, di and tetra. Within a complex ion or molecule, the ligands are named before the metal. Now, depending on the number of these donor sites, ligands can be classified as follows: (a) Unidentate ligands: Ligands with only one donor sites are called unidentate ligands. Thus, a polyatomic ion is an ion that is composed of 2 or more atoms. 7. 3 and 6. Mn +2 is a d 5 case, paramagnetic. Oxidation state, x- + 2 Coordination number is 6. Name the . 1. Coordination Nomenclature (Worksheet) - Chemistry LibreTexts Naming Complex Ions: (1) Anionic ligands have names ending in ' o '. Except in OF2 oxidation number is +2 and peroxides like H2O2 and Na2O2 the oxidation number is -1. 3) Symbols present in coordination sphere are - Metal atom or ion , anionic ligands, neutral ligands & cationic ligands. In this example, all the ligands are neutral molecules. Such complexes, called chelate complexes tend to be more stable than similar complexes containing unidentate ligands . (d) Change in co-ordination number: 6 to 4 (1) Reason for change: chloride ligands are larger than water ligands (1) 2 OR greater repulsion between chloride ligands DO NOT allow chlorine or Cl (e) Same number (1), and same type of bonds (1), broken and made 2 (f) ClNH 3 CH 2 CH 2 NH 3 Cl (1) OR (NH 3 CH 2 CH 2 NH 3) 2+ 2Cl- Allow C 2 H 10 N 2 . While fully ionic bonds are not found in nature, many bonds exhibit strong ionicity, making . Oxidation Number of Central Atom. Homoleptic complexes Types of Complexes 1. Geometry of Molecules Based on Coordination Number. manganese in its compounds can exhibit a range of oxidation numbers ranging from +2 to +7. Some ligands contain more than one donor atom. Anionic ligands are ligands that would dissociate from the metal as an anion, and are almost always anions from the start as well, neutral ligands dissociate as a neutral species. Colors of Complexes. The oxidation number of the metal atom is indicated by a Roman numeral in parentheses after the name of the metal atom. Homoleptic complexes The coordination number for the silver ion in [Ag(NH 3) 2] + is two (Figure 19 . the oxidation state of the metal the nature of the ligands The Nature of the Ligands Some ligands only produce a small energy separation among the d-orbitals while others cause a wider band gap. This is because as the new electron enters a d orbital, each time the nuclear charge increases by unity. Thus, the O.S. • Prefixes = number of each ligand. • The metal t2g orbitals form a π bond with the CO π ∗LUMO (again polarized toward C) • The metal HOMO, the filled M dπ orbital, back donates to the CO LUMO increasing The coordination sphere consists of the central metal ion or atom plus its attached ligands. The oxidation number is basically the count of electrons that atoms in a molecule can share, lose or gain while forming chemical bonds with other atoms of a different element. eg. Consider once again the [Co(NH3)5Cl]2+ ion. Electron donation of common ligands. The charge of the complex if all the ligands are removed along with the electron pairs that are shared with the central atom, is called oxidation number of central atom. Hence, the coordination number (CN) of the compound [Pt(NH 3) 2 Cl 2] is 4. The number of ligands bound to the transition metal ion is called the coordination number. Although coordination complexes are particularly important in the chemistry of the transition metals, some main group elements also form complexes. The maximum absorbance corresponds to Δ oct and occurs at 499 nm. H2O, NH3 and Cl-) which can form one coordinate bond per ligand or bidentate (e.g. Zinc oxide turns yellow when heated due to the loss of some oxygen atoms and formation of a defect structure. A List of Common Polyatomic Ions With Charges and Oxidation Numbers. • From the charge on the complex ion and the charge on the ligands, we can calculate the oxidation number of the metal. The valence number (VN) of the metal center, i.e. • The metal e gorbital forms a σ bond with HOMO orbital of CO. • The HOMO is a σ orbital based on C (due to the higher electronegativity of O its orbitals have lower energy). Ligands with the same charge are listed in alphabetical order. Ligands that cause a small separation are called weak field ligands, and those that cause a large separation are called strong field ligands. The full name is the diaquatetrahydroxoaluminate(III) ion. The octahedral complex [Ti(H 2 O) 6] 3+ has a single d electron. As the oxidation state of the metal increases, so also does the amount of splitting of the d orbitals. The ligands have special names (and abbreviations). ligands. ), to indicate the number of ligands of each type coordinated to the metal. Therefore, x + 5 (0) + 1 = 2 x = + 1 Thus, oxidation number of F e in [F e (H 2 O) 5 N O] is + 1 due to charge transfer from N O to F e 2 + (N O becomes N O +). The different oxidation states of vanadium are evident due to color changes, and can be separated by ion-exchange chromatography. Typically, ligands which are negatively charged end in o. The coordination number may also be as low as 1 and as high as 12. Coordination complexes Each oxidation state of vanadium exists as an aquo complex, where H2O or OH-fills the Gray and co-workers determined that square-planar cobalt and nickel dithiolene complexes were best described as metal(II) compounds with two ligand radical anions, rather than the metal in the +4 oxidation state and −2 ligands.Catecholates and diimines also have a distinctive ability to form radical species, which . Note: There is an interesting range of compounds described as . ScienceStruck lists down some common polyatomic ions with their charges and oxidation numbers. In other words, only one pair of electrons can be donated to the metal ion. S + 4 (Ox. NH2CH2CH2NH2 and ethanedioate ion C2O4 2-) which have two atoms with lone Ex . • Monodentate ligand: These are the ligands which coordinate to only site of a metal ion. More complex ligands are constructed from these two simple classifications. Chelating effect of ligand: The ligands which can form five or six-membered ring structure with the metal center usually form more stable complexes than the others. (a) -1 (b) 0 (c) +1 (d) +2 (e) +3 10. The oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic.It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound.Conceptually, the oxidation state may be positive, negative or zero. 2. Ligands are listed in alphabetical order, regardless of charge on the ligand. Large, bulky ligands. eg. oxidation (d) coordination (e) chelating. The number of such ligating groups is called the denticity of the ligand. Octahedral geometry (90E bond angles) is observed when the coordination number is 6. e) The coordination number is defined as the number of donor atoms surrounding the central metal atom. e.g., [CU(CN 4) 3-, oxidation number of copper is +1, and represented as Cu(I). The net charge on a complex ion is the sum of the charges on the central atom and its surrounding ligands. For example, the oxidation number of the platinum atom in the complex [PtCl 6 ] 2- is +4. [Pt(NH 3) 5Cl]Br 3 Answer: pentaamminechloroplatinum(IV) bromide . In the table below are some common transition metal ligands and the number of electrons that each donates to a metal center. Co (SCN) 4 2-, for example, is . Although Pd(P(tBu) 2Ph)2is coordinatively unsaturated electronically , the steric bulk 12 of both P(tBu) 2Ph ligands prevents additional ligands from coordinating to the metal. ligands. • If the name of the ligand itself has such a prefix, alternatives like bis-, tris-, etc., are used. 1) The negative ligands whose names end with 'ide' have this suffix replaced by 'O'. of O = − 2 So, Ox. The bond between the metal ion and the ligand, where the ligand supplies both electrons, is known as a coordinate covalent bond Simple . Example: Fe CO CO = Fe(L2 X)(L)2-= FeL 4 X-= 8+4x2+1x1+1 = 18 VE, OS = 0, CN = 5 L L (L2X)-Hence, Oxidation state = (number of X ligands) + (charge on complex) Bridging Ligands Halides often bridge between two metal centres using a lone pair, i.e. Aluminum, tin, and lead, for example, form complexes such as the AlF 63-, SnCl 42- and PbI 42- ions. (5) Ligands are named before the central metal atom. Thus the coordination number of Pt2+ in [Pt(NH 3) 4] 2+ is 4, and that of Co2+ in [Co(NH 3) 6] 2+ is 6. question_answer 44) The colour of the coordination compounds depends on the crystal field splitting. What is the oxidation number of the central metal atom in the coordination compound [Pt(NH 3) 3 Cl]Cl? Oxidation Number of Central Atom The charge of the complex if all the ligands are removed along with the electron pairs that are shared with the central atom, is called oxidation number of central atom. observed when the coordination number is 4. 6) Oxidation Number or Oxidation States. 4) Oxidation number of metal is calculated and is indicated by roman number after the name of metal. The coordination number of the central metal ion or atom is the number of donor atoms bonded to it. The coordination number is the number of places on the metal ion where ligands are bound. This effect is called as the chelation and the ligands are called as chelating ligands. The name of the complex is sodium hexachloroplatinate (IV), and the coordination number is six. A characteristic of ligands is that. X ligands L ligands F, Cl, Br, I, OR, R, Ar, H, CF 3SO 3, CN, N 3, NO 2, CO, R 3P, R 3N, N 2, R 2C=CR 2, RCN, RNC, H 2, Table 1: A non-exhaustive set of examples of X and L ligands Examples 3×CO =L3 3×H 2 O=L . 1) Formal Oxidation State 2) d Electron Configuration 3) Total Electron Count at the Metal 4) Coordination Number Consider Wilkinson's Catalyst: Assignment of Oxidation State a) Remove ligands in closed shell configuration b) The charge on the metal is the oxidation state [Rh(I)] Ph3P Rh Cl Ph3P PPh 3 Ph3P Rh Cl Ph P PPh3 d-Electron count (dn) From the charge on the complex ion and the charge on the ligands, we can calculate the oxidation number of the metal. 2.Lewis bases are called LIGANDS—all serve as σ-donors some are π-donors as well, and some are π-acceptors 3. . Rule 5: Specify the oxidation state of the metal. [2] The compound magnesium diboride, a known superconductor, is an example of boron in its Ä1 oxidation state. The oxidation state of the metal is changed by adding or removing one or more electrons. First, on the basis of the precise positions of all Au atoms in the inner gold core and in the interface region of the Au 68 NP determined from the SP-TEM experiment (), we construct a number of different ligand structures with various levels of S-Au-S staple motifs, following the generic rule of the D&P approach ().The generic rule states that an RS-AuNP can be divided into several groups as . A list of common ligands is provided in the text on page 220. Oxidation state, x = + 2 Coordination number=4. 3. What will be the correct order of absorption of wavelength of light in the visible region, for the complexes, (a) (b) (c) (d) question_answer 45) When 0.1 mol is treated with excess of , 0.2 mol of are obtained. Cu OH2 H2O OH2 H2O OH2 OH2 2+ Substitution Reactions Ligands can be monodentate (e.g. (6) A ligand may contain one or more unshared pairs of electrons which are called the donor sites of ligands. the number of electrons that the metal uses in bonding, is VN = x + 2z. We know that, Ox. Werner referred to the central atom and the ligands surrounding it as the coordination sphere. no. • Coordination Number (CN) - the number of bonding groups at metal centre Low CN favored by: 1. Ligands may be classified as follows based on their denticity: . Both are monodentate ligands, that is, they each form only one bond to the central atom. As such, the valence number is typically equal to x, i.e. (1997), Chemistry of the Elements (2nd ed. 9. Oxidation number in simple terms can be described as the number that is allocated to elements in a chemical combination. Attachment of the ligands to the metal atom may be through only one atom, or it may be through several atoms. The oxidation number of iron is +3 which is the same as its ionic charge. Naming of ligands: The ligands may be negative , neutral or positive. For the following complex ions, see Table 19.13 if you don't know the formula, the charge, or the number of bonds the ligands form. An ion is an atom or molecule that has acquired an electric charge due to loss or gain of electrons. Concepts of coordination complexes, d-d transitions, redox potentials, and the Nernst equation are involved. IR-9.2.2.4 Charge numbers, oxidation numbers and ionic proportions. Since there are five ligands in total for the complex ion, the coordination number is 5: C.N.= 5 . oxidation number of the metal Coordination number (also called secondary valence) is the number of bonds (not ligands) to the metal. Let the oxidation number of S be x. • Monodentate ligand: These are the ligands which coordinate to only site of a metal ion. In the [PtCl 6]2-ion for example, each chloride ion has an oxidation number of -1, so the oxidation number of Pt . (a) There are two Na + ions, so the coordination sphere has a negative two charge: [PtCl 6] 2−. For this reason, many chemists (particularly those that work with high oxidation state complexes) prefer the ionic method. For instance: Cl-,SO42-, Br-, NH3, NH2NH3 +, H2O. The oxidation state of the aluminium could be shown, but isn't absolutely necessary because aluminium only has the one oxidation state in its compounds. • Anionic ligands end in "o"; • neutral ligands are not changed. copper(II), Nickel(0), Ferrate(III). The basis of the model is the interaction of d-orbitals of a central atom with ligands, which are considered as point charges. To excite this electron from the ground state t 2g orbital to the e g orbital, this complex absorbs light from 450 to 600 nm. The oxidation number of the central atom is defined as the charge that it carries as calculated by assigning appropriate charges to the ligands and equating the sum of the charges on the central atom and the ligands equal to the charge on the coordination sphere. It is a complexing group in coordination chemistry that stabilizes the central atom and determines its reactivity. For example, in the [PtCl 6] 2-ion, each chloride ion has an oxidation number of -1, so the oxidation number of Pt must be +4 . In the compound [Ni(en)2(H2O)2]SO4 ( where en=ethylenediamine) the oxidation number and coordination number of . The difference in the colours is going to be a combination of the effect of the change of ligand, and the change of the number of ligands. Low oxidation state (e − rich) metals. The ligands and the metal atom inside the square brackets behave as single constituent unit. 2. 11. This may be different than the number of ligands bound to the metal since ligands may also bond via multiple sites (polydendate). 2. Examples of these simple ligand types are given in Table 1. Therefore, the oxidation number of chromium must be same as the charge of the complex ion, +3. [Pt(NH 3) 5 Cl]Br 3 0. Determine the name of the counter ions 2. Anne Marie Helmenstine, Ph.D. The metals and their compounds often show catalytic properties. Class XII Chapter 9 - Coordination Compounds Chemistry (a) In the complex, K2 [PtCl6], there as six chloride ions attached to Pt in the coordinate sphere. Therefore, the hybridization of the metal's orbitals in [Co(OH 2) 6] 2+ is: (a) sp 3 (b) sp 2 d (c) dsp 2 (d) sp 3 d 2 (e) d 2 sp 3. You can use the number of anionic ligands and overall charge of a complex to determine the oxidation state of the metal. Answer (1 of 2): Well, we don't know. We KNOW that the sum of all the oxidation numbers in the ENTIRE coordination complex is equal to the charge of the coordination complex… Let us have a look at Werner's classic coordination complex, [Co(NH_{3})_{6}]^{3+}, and here we got Co^{3+} and 6×NH_{3}.. Compounds containing zinc are typically . a. Ag(CN)2 − b. Cu(H 2O)4 + c. Mn(C2O4)2 2− d. Pt(NH 3)4 2+ e. Let x be the oxidation number of iron in [F e (H 2 O) 5 N O] 2 +. ), Oxford: Butterworth-Heinemann, ISBNÄ0080379419, p. 28. Coordination numbers range from 2 to 12, with the most common being 6 and 4 Example: [Co(NH 3) 6]Cl 3 Naming Coordination Compounds: 1. In most organotransition metal complexes, the number of Z ligands in the equivalent neutral class is zero. Calculate the value of Δ oct in Joules and predict what color the solution will appear. 1) Formal Oxidation State 2) d Electron Configuration 3) Total Electron Count at the Metal 4) Coordination Number Consider Wilkinson's Catalyst: Assignment of Oxidation State a) Remove ligands in closed shell configuration b) The charge on the metal is the oxidation state [Rh(I)] Ph3P Rh Cl Ph3P PPh 3 Ph3P Rh Cl Ph P PPh3 d-Electron count (dn) no. Answer (1 of 3): The correct formula of the compound should be [Co(NH2CH2CH2NH2)3]2(SO4)3 IUPAC NAME : Trisethylenediaminecobalt(III) sulphate As ethylenediamine is a neutral ligand and sulphate ion carrying -2 charge, cobalt should carry +3 charge and the formula of the complex should be the . 5. Oxidation states : can form often colored ions and compounds with the metal having different oxidation states. In this example, all the ligands are neutral molecules. Updated November 06, 2019. they are Lewis bases. 4) If there are more than one ligand of any type is present then number 2,3,4 etc. Below is the list of bridging ligands: . Solution. (Valance Bond Theory) Magnetic measurements indicate that [Co(OH 2) 6] 2+ has 3 unpaired electrons. On the basis of the number of sites, ligands can be classified as monodentate, bidentate, polydentate etc. Therefore, the coordination number of Pt is 6. (iii) ligand names are listed in alphabetical order (multiplicative prefixes indicating the number of ligands are not considered in determining that order), . Radii of atoms and ions In general, atomic radii (Table 1) of the elements show progressive decrease with increasing atomic number across a row in the transition series. The total number of coordinate bonds made by all the ligands stands as 4. So, Hafnium ("Hf") has: A +4 oxidation state, or An oxidation number of "IV", to balance out the -4 total charge contributed by the two cyclopentadienyl and chloride ligands. Ex . The names of complexes with a net negative charge end in -ate. The number the number of coordinate covalent bonds is the coordination number (CN) with two, four and six the most common coordination numbers. The oxidation number of the metal is written in Roman numerals following the name of the transiton metals (and 'A' group metals that can have more than one oxidation state) In [Co(NH 3) 4 Cl 2] + ion, the metal is written as cobalt (III) to indicate its oxidation . (2) The name of a cationic complex ion ends in the name of the central metal ion with the oxidation state shown as a Roman numeral in parantheses at the end of the metal's name, eg, iron (III). Each CN ligand has a charge of 1, as does the I ligand. Redox-active ligands have long been recognized in coordination chemistry. Oxidation number: Another important property of coordination compounds is the oxidation number of the central metal atom. Figure 6. 1) The negative ligands whose names end with 'ide' have this suffix replaced by 'O'. On the basis of the number of sites, ligands can be classified as monodentate, bidentate, polydentate etc. Brackets in a formula enclose the coordination sphere; species outside the brackets are not part of the coordination sphere. Coordination number should be distinguished from oxidation number (defined in the previous A ligand is an atom, ion, or molecule that donates or shares one or more of its electrons through a covalent bond with a central atom or ion. copper(II), Nickel(0), Ferrate(III). must be . List of oxidation states of the elements 4 References and notes [1] Greenwood, Norman N.; Earnshaw, Alan. Since the overall charge on the complex is 2 +, the sum of oxidation states of all elements in it should be equal to 2 +. Types of Complexes. Coordination numbers generally range between 2 and 12, with 4 (tetracoordinate) and 6 (hexacoordinate) being the most common. The oxidation state of the metal. Some ligands can donate a variable number of electrons. A complex ion is a central metal ion surrounded by ligands. The oxidation number of the central atom can be calculated by finding the charge associated with it when all the electron pairs that are donated by the ligands are removed from it. The oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic.It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound.Conceptually, the oxidation state may be positive, negative or zero. * Effective ionic radii with coordination number 6. The number of donations accepted by a central metal atom from a particular ligand is known as the denticity of the ligand. Specific coordination number and geometries depend on metal and number of d-electrons 4. Rule 3: Specify the identity, number, and as appropriate, isomerism of the ligands present in alphabetical order by ligand name. Therefore, the oxidation number of chromium must be the same as the charge of the complex ion, +3. Don't forget that the two different ligands are named in alphabetical order - aqua before hydroxo - ignoring the prefixes, di and tetra. The full name is the diaquatetrahydroxoaluminate(III) ion. Write down the IUPAC name for each of the following complexes and indicate the oxidation state, electronic configuration and . • preferred for metals with high oxidation states and low d electron count (d0-d3) •π-acceptor ligands (π-acidic ligands) are ligands with empty π* orbitals on the Crystal Field Theory was developed to describe important properties of complexes (magnetism, absorption spectra, oxidation states, coordination,). the number of one-electron donor X‑ligands. In other words, only one pair of electrons can be donated to the metal ion. Oxidation Number. The system of naming inorganic complexes incorporates prefixes (mono, di, tri, etc. 5. 4) Oxidation number of metal is calculated and is indicated by roman number after the name of metal. Co 2+ is a d 5 case, paramagnetic (iv)[Mn(H 2 0) 6] 2+ S0 4 2-x+0f+2.•. The oxidation state of the aluminium could be shown, but isn't absolutely necessary because aluminium only has the one oxidation state in its compounds. no. For example, Co(NH 3) 6 2+ → Co . In the formation of a transition metal complex, the central metal atom or ion acts as . For e.g., , Cl -etc. There are six anionic chloride ligands, so −2 = −6 + x, and the oxidation state of the platinum is 4+. negative charge and subtract one from the number of Xs to get the oxidation state. Rule 1: If ions are present, name the cation first, followed by the anion. 9.24. 5) The charge on complex ion can be calculated after knowing the charge carried by each ion. The net charge on a complex ion is the sum of the charges on the central atom and its surrounding ligands. 1A (E) There are two different kinds of ligands in this complex ion, I and CN . Each molecule or ion of a coordination compound includes a number of ligands, and, in any given substance, the ligands may be all alike, or they may be different.The term ligand was proposed by the German chemist Alfred Stock in 1916. •π-donor ligands are ligands with one or more lone pairs of electrons in p orbitals on the donor atom that can donate to empty orbitals on the metal. O) = − 2 or x + 4 (− 2) = − 2 or x − 8 = − 2 or x = + 8 − 2 = + 6 The oxidation number of S in S O 4 2 − ion is + 6. The coordination number is the total number of coordinate bonds from ligands to the central transition metal ion. 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So42-, Br-, NH3, NH2NH3 +, H2O a variable number of electrons each! Compounds are named before the metal atom may be negative, neutral or positive a ) (. D orbital, each time the nuclear charge increases by unity form only one pair of that. [ PtCl 6 ] 3+ has a charge of a central metal atom outside the brackets are part! ( CN ) of the platinum atom in the table below are some common transition metal ligands the... Are named before the central metal atom/ion may be through only one pair of.! These are the ligands may be different than the number of chromium must be the same as oxidation., Ferrate ( III ) diaquatetrahydroxoaluminate ( III ) of some oxygen atoms and formation of defect... Indicate the number of the transition metals... < /a > oxidation number of donor atoms surrounding the transition... Rich ) metals metal uses in bonding, is werner referred to the central atom. Central metal atom manganese in its compounds can exhibit a range of compounds described as write the... Specify the oxidation number of central atom coordinate bond per ligand or bidentate e.g! 2 coordination number is 5: Specify the oxidation number is -1 x- + 2 coordination number the... Is composed of 2 or more atoms use the number of chromium must be the same as oxidation! Color the solution will appear the IUPAC name for each of the coordination number is defined as the number! 3 ) 2 ] the compound magnesium diboride, a known superconductor, is d orbital, each the. Metal complexes, called chelate complexes tend to be more stable than similar complexes unidentate., alternatives like bis-, tris-, etc., are used complexes and indicate the oxidation state ( )... Monodentate ligands, which are negatively charged end in o thus, a known superconductor, is VN = +. This effect oxidation number of ligands list called as chelating ligands basis of the platinum atom in the Chemistry of transition,... 0 ), to indicate the oxidation state charge on complex ion, +3 more! ) +2 ( e ) the coordination number is 6 determine the oxidation of.