Chemistry CH3

Polyatomic Ions

- A polyatomic Ion, is a cation or Anion that contains more than one atom. They are held together by covalent bonds, but since the ion bears a charge (The total number of electrons it contains is different from the total number of protons in the nuclei of all atoms), it bonds to other ions by ionic bonding Two polyatomic cations -H3O+ the hydronium ion- acid based chemistry -NH4+, the ammonium ion- Polyatomic Anions: -Most contain a nonmetal -Carbonate (CO3^-2), Sulfate (SO4^2-), and Phosphate (PO4^3-) -Most end in -ate, except hydroxide (OH-) and cyanide (CN-) --The suffix -te is used for an anion that has fewer oxygen atom than a similar anion named with the -ate ending. Thus, SO4^2- is sulfate, but SO3^2- is sulfite --When two anions differ in the presence of a hydrogen, the qword hydrogen or the prefix bi is added to the name of the anion. Thus, SO4^2- is sulfate, but HSO4^- is hydrogen sulfate or bisulfate

Naming Anions

--Anions are named by replacing the ending of the element name by the suffix- ide CI (Chlorine)= Ci- (Chloride) O (Oxygen)= 0^2-= Oxide

Naming Ionic Compounds

--Chemical Nomenclature: Assigning unambiguous name to each compound --Cations of main group are given the name from which they are formed --Ion is common to add after the same of the metal cation to distinguish it from the neural itself --When a metal is able to form 2 different Cations: --Method (1.): Follow the name of the cation by a Roman numeral in parentheses to indicate its charge --Method (2): Use the suffix- ous for the cation with the lesser charge and the suffix -ic for the cation with the higher charge. These suffixes are often added to Latin names of the elements Fe2+= Iron (11) or Ferrous fe3+= Iron (111) or ferric

What are some ionic compounds added to foods to prevent disease or maintain good health?

--Potassium Iodine (KI): Added to table salt because Iodine is needed to synthesize thyroid hormones --Sodium Fluoride (NaF): Added to toothpaste to strengthen tooth enamel and prevent tooth decay --Potassium Chloride (KCI): Given to help maintain proper fluid balance and organ function

Writing a formula with an Ionic Compound

1. Identify which element is the cation and which is the anion --Metals form cations and nonmetals form anions -Use group number of a main element to determine the 2. Determine how many of each ion type are needed for an overall charge of zero -When the cation and anion have different charges, use ion charges to determine the number of ions of each needed -The charges on the ion tell us how many of the oppositely charged ions are needed to balance charge 3. Write Formula: Place the Cation first and then the anion and omit the charges -Use subscripts to show the number of each ion needed to have zero overall charge -When no subscript is written, assume it to be 1 -

Sample Problem Writing the formula for an ionic compound that contains a polyatomic ion

Q: Supplement consists of an ionic compound formed from calcium and phosphate. What is the formula? 1. Identify the cation and Anion and determine their charges -Calcium is the cation, and has a charge of +2 (ca^2+) -Phosphate is a polyatomic Anion with a -3 charge (PO4^3-) 2. Balance the charges: -The charges are unequal, so the ions tell us how many oppositely charged ions are needed to balance charge Ca3(PO4)^3- 3. Write the formula with the cation first and then the Anion, use subscripts to show the number of each ion needed -To balance charge, three Ca^2+ cations are needed for two PO4^3- anions, so the formula is: Ca3(PO4)2

How to determine if compounds are ionic or covalent?

--The position in the periodic table determines the type of bonds they form: 1. When a metal and nonmetal combine, the bond is ionic 2. When two nonmetals combine, or a metalloid bonds to a nonmetal, the bond is covalent In molecular Art: --An element is composed of spheres of the same color, where a compound is composed of spheres of different colors --A molecule is a compound or element that contains covalent bonds

Naming Ionic Compounds with Cations from Main Group Metals

--To name an ionic compound with a main group whos charge never varies, name the cation and then the Anion. DO not specify that charge on the cation, do not specify how many ions of each type are needed to balance the charge Na+ F- = NaF (sodium fluoride) Mg+ CI- = Magnesium Chloride baCI2= Barium chloride (not barium dichloride) Sample Problem: Naming an Ionic Compound that contains a main group metal: Na2S & AIBr3 1. Name the Cation and then the Anion --Na2S: the cation: Sodium; Anion: Sulfide (derived from sulfur, thus has the name Sodium Sulfide --AIBr3: The Cation: Aluminum; Anion: Bromide (derived from bromine; the name is Aluminum Bromide

Naming Ionic Compounds that contain a polyatomic Ion

--in table 3.5: Names of common polyatomic ions Name each ionic compound: A: NaHCO3 &B: AI2(SO4)3 1. Determine if the cation is fixed or a variable change. To name an ionic compound that contains a cation that always has the same charge, name the cation and then the anion. When a metal has a variable charge, use the overall anion charge to determine the charge to determine the charge on the cation. The name the cation (using a roman numeral or the suffix -ous or ic followed by the anion. Solutions a: NaHCO3: Sodium ions have a fixed charge of +1. The anion HCO3^- is called bicarbonate or hydrogen carbondate Answer: Sodium Bicarbonate or sodium hydrogen carbonate b. AI2(SO4)3: Aluminum cations have a fixed charge of +3. The anion SO4^2- is called sulfate Answer: Aluminum Sulfate

Physical properties of Ionic compounds

-Are crystalline solids composed of packed ions to maximize the interaction of the positive charge of the cations and negative charge of the anions -Size and charge are determined by the way they pack crystal lattice -Ionic solids are held together by strong interactions of oppositely charged ions. --Ionic compounds have a high melting point because in order to form a liquid, it takes a lot of energy to separate the tightly held together ions -Ionic compounds have extremely high boiling points because a lot of energy is needed to overcome attractive forced in the liquid phase to form ions that are far apart and disorganized in the gas phase -Many ionic compounds are soluble in water because the ions separate and each cation and anion is surrounded by water molecules which give the ions the energy it needs to overcome the strong ionic attraction of crystalline lattice -Dissolved ionic compounds in water have an aqueous solution that conducts electricity (only ones that form ions in dissolved water conduct electricity)

Ions

-Cations: Are positively charged ions. A cation has fewer electrons than protons -Anions are negatively charged ions. An anion has more electrons than protons - To form an ion, an atom of a main group element loses or gains an electron to obtain the electron configuration of the noble gas closest to it in the periodic table, this forms ions to have stable electronic arrangement with a completely filled shell of electrons ---Example: NA- (1s^22s^22p^63s^1 loses an electron: 1e- to form a sodium cation: Na+: 1s^22s^22p^6 (8 electrons in outer shell) -Metals form Cations -By losing one, two, or three electrons, an atom forms a cation with a completely filled outer shell of electrons -Cations are smaller in size than the atoms from which they are formed. Because a cation has more protons than electrons, the positively charged nucleus pulls the remaining electrons closer --Chlorine: 1s^22s^22p^63s^(2)3p^(5): 7 electrons in the outer shell: It gains an electron (1e-) to form 8 electrons in the outer shell: 1s^22s^22p^63s^(2)3p^(6): CI- (Chloride Anion) -Nonmetals form anions -By gaining one, two, or three electrons, an atom forms an anion with a completely filled outer shell of electrons -Anions are larger than the atoms from which they are formed. Because an anion has more electrons than protons, the electrons are held less tightly by the positively charged nucleus, and the anion size is larger than the atom size -Octet Rule: s and p orbitals are filled: A main group element is especially stable when it possesses an octet of electrons in its outer shell

Writing an ion symbol by counting protons and electrons

-Count the number of protons to determine the atomic number and the identity of the element -Compare the number of protons with the number of electrons to determine the charge. When the number of protons is greater than the number of electrons, the ion has a net positive charge. When the number of electrons is greater than the number of protons, the ion has a net negative charge Writing an Ion symbol: -When the number of protons equal the atomic number, this quality identifies the element -The charge is determined by comparing the number of protons with electrons. If electrons are greater than protons, the charge is negative (anion). If the number of protons is greater than electrons, the charge is positive (cation) Ca 2+= 20 protons (Atomic number) and 18 electrons, 2 more protons than electrons, 18 electrons O 2-: 8 protons (atomic number) and 10 electrons: , the charge is -2, so there are 2 more electrons than protons, giving the ion 10 electrons

Relating Group Number to Ionic Charge for main group elements

-Elements in the same group form ions of similar charge -Group 1A: one valence electrons: M+ + 1e- -Group 2A: two valence electrons: M2+ +2e- -Group 3A: 3 valence electrons M3+ + 3e- -Metals form cations. For metals in group 1A, 2A, 3A, the group number= the charge of the cation -Li+, Be+ have a 1s^2 electronic configuration making them especially stable because they have a filled outer shell of electrons, although they do not have an octet of electrons -Nonmetals for anions. For nonmetals in groups 5A, 6A, and 7A, the anion charge= 8- (the group number) --5A (5 valence electrons) + 3e- {anion charge= 8- (group number= 3) (3-) ( A gain of electrons forms a anion with a - charge; A loss of electron forms a cation with a + charge)

Intro to bonding

-Ionic compounds: Composed of negative and positively charged ions held together by electrostatic forces (the electrical attraction between opposingly charged ions)- NaCI/ CaCO3 -Covalent Bonds: Composed of individual molecules, discrete groups of atoms that share electrons (H2O)/ CH4 -Bonding is the joining of two atoms in a stable arrangement -Bonding is favorable bc, it always forms a more stable compound -Noble gases do not readily react to form bonds -In bonding, the elements gain, lose, or share electrons to attain the electron configuration of the noble gas closest to them on the periodic table -Ionic Bonds: Result from the transfer of electrons from one element to another -Covalent Bonds: Result from the sharing of electrons between two atoms -Ionic bonds form between a metal on the left side of the periodic table and a nonmetal on the right side -Since ionic compounds are composed of ions- charged species in which the number of protons and electrons in a atom is not equal -Covalent Bonds: Are formed when two nonmetals combine, or when a metalloid bonds to a nonmetal -A molecule is a compound or element containing two or more atoms joined together with covalent bonds

Health and Medicine Focus: Useful Ionic compounds

-Ionic compounds= active ingredients in drugs like calcium carbonate (CaCO3), Magnesium Hydroxide [Mg(OH)2] or Iron (II)Sulfate (FeSO4) --Bicarbonate (HCO3- Polyatomic anion that controls the acid base balance in blood --Magnesium Sulfate (mgSO4): prevents seizures caused by extremely high blood pressure associated with some pregnancies --70% of bone is composed by a complex ionic solid with the formula: Ca10(PO4)6(OH)2- hydroxyapatite --Sodium alendronate-Fosamax: decreases bone loss formula: Na(C4H12NO7P2) (Sodium cation: NA+ and polyatomic anion (C4H12NO7P2)^-

Writting Formulas for Ionic Compounds with Polyatomic Ions

-Is no different than writing a formula for an ion with a single charged atom --When the cation and anion have the same charge, only one of each is needed for an overall charge of zero Na+ + NO2^- (one atoms of each is needed to balance the charge) =NANO2 (Sodium Nitrate) Ba^2+ + SO4^2- (One of each ion is needed to balance the charge)= BaSO4 --In a compound formed from ions of unequal charges, the charges on the ions tell us how many of the oppositely charged ions are needed to balance the charge Mg^2+ + OH^- (The charges are not equal, +2 and -1. Two OH- Anions are needed to balance charge): Mg(OH)2 - Use parentheses around all atoms of an ion and use subscript outside the parentheses --Parentheses are used around a polyatomic ion and a subscript indicates how many of each are needed to balance the charge. The formula is written as Mg(OH)2 (not MgO2H2 or MgOH2)

Important Ions in the human body

-Na+, K+, Ca+, Mg+ -Fe2+ and CI-

Naming Ionic compounds containing metals with variable charge

-Specify the charge of the Cation -Formula of ionic compound- that is how many cations are there per anion- allows us to determine the charge of the cation Name for CuCI2? 1. Determine the charge on the cation -Two CI anions, each one has a -1 charge, the copper cation must have a =2 charge to make the overall charge zero CuCI2= total negative charge is -2; Cu+2 must be to balance the charge 3. Name the Cation and Anion -Cation= its element name followed by a roman numeral to indicate its charge. In common system, use: -ous or- ic to indicate charge -Name the Anion by changing the ending of the element to the suffix- ide Cu2+= copper (II) or cupric CI-= Chloride 3. Write the Name of the Cation first, then the Anion -Answer: Copper(II)Chloride or Cupric Chloride

Metals with Variable Charge

-Transition metals= Cations= losing electrons -Can be +2= 2 electrons lost in the s orbital; +3= 2 electrons lost in the S orbitals, 1 electron lost in the d orbital --Because transition metal cations have additional d electrons that its nearest noble gas is missing, the octet rule is not followed

Ionic Compounds

-When a metal (left or right side) transfers one or more electrons to a nonmetal (on the right side), ionic bonds are formed -Ionic Compounds are composed of cations and anions -Ions in ionic compounds are arranged to maximize the attractive force between the oppositely charged species -Positively charged cations are located closer to the charged particles to which they are attracted- anions- and further from the particles from which they are repelled- cations --The sum of the charges in an ionic compound must always be zero overall --Ionic formula shows the ratio of ions that combine to give zero charge -When Ca(+2) combines with fluorine (-), there must be two F(-) anions for each Ca+ to have an overall charge of zero -Use subscripts when the number of ions needed to achieve zero charge is greater than 1

Naming An Ionic compound derived from metals that have fixed or variable change

1. SnF2 2. AI2o3 Analysis: -Determine if the cation has a fixed or variable charge -Ionic compound that contains a cation that always has the same charge, name the cation and then the anion (-ide). -When metal has a variable charge, use overall anion charge to determine the charge on the cation. Then name the cation (-ous or -ic) followed by the anion Solution: (1) SnF2: Sn cations have variable charge, so the overall anion charge determines the cation charge -SnF2= =2 charge (tin (II) or stannous) to balance -2 charge of anions (fluoride) Answer: tin(II) or Stannous Fluoride Solution (2): AI2O3 has a fixed charge of +3. To name compound, name the cation as the element (aluminum) and the anion by changing the ending of the element name to (ide= oxide) Answer: Aluminum Oxide

Writing a formula from the name of an Ionic compound

Compound: tin(IV) oxide Step 1. Identify the cation and anion and determine their charges -Cation appears first, then anion -for metal with variable charge, the roman numeral gives the charge of the cation --Tin= Cation, roman numeral IV= +4, making SN4+. Oxide is the name of the oxygen anion, O2 Step 2: Balance the charges -Use the charge on the cation to determine the number of ions of the anion needed to balance the charge Sn4+ and O2-= two anions are needed for each +4 cation Step 3: Write the formula with the cation first, and use subscripts to show the number of each ion needed to have zero overall charge: SNO2

Deriving a formula from the name of an ionic compound example

Write a formula for sodium oxide Analysis: 1. --Identify the cation and the anion and determine their charges Because the name of the cation appears first, sodium is the cation and oxide is the anion. Sodium has a fixed charge of +1 (Na+) and oxide has a charge of -2 (O2-) --2. Balance the charges Use the charge on the anion to determine the number of ions of the cation needed to balance the charge -Two 1+ cations are needed for each 2- anion 3.-- Write the formula with the cation first, and use the subscripts to show the number of each ion needed To balance the charge, two Na+ cations are needed for each oxide anion (O2-) so the formula of sodium oxide is : Na2O