Occurs when electrons are transferred electrostatic attractions (btw positive & negative atoms)

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2 Ionic Bonding

3 Ionic Bonding Occurs when electrons are transferred from one atom to another, forming two ions The ions stay together because of electrostatic attractions (btw positive & negative atoms) Ionic bonds form easily between alkali metals and halogens

4 The Octet Rule Atoms tend to gain, share, or lose electrons in order to obtain a full set of valence electrons (in most cases this equals 8) An octet of electrons consists of full s and p sublevels on an atom. Exceptions: transition elements and rare earth elements

5 Example + - Na + Cl Na + Cl

6 Properties of Ionic Compounds Ionic compounds do not form molecules; they form a crystal lattice The green spheres are Na + and the red spheres are Cl -

7 This is a crystal of CaCl 2. Each ion is held rigidly in place by strong electrostatic forces that bond it to several oppositely charged ions

8 Other Properties Normally form between metals and nonmetals Ionic compounds have ions that form very strong bonds, which makes them hard and brittle They have high melting points and high boiling points When dissolved in water, the solution will conduct electricity

9 Types of Ions There are two types of ions Monatomic: cation or anion that consists of a single atom. Examples: Na + and Cl - Polyatomic: two or more atoms that act as a single ion (or particle). Examples: (CO 3 ) 2- and (OH) -

10 Types of Ionic Compounds Ionic compounds will be a combination of a metal and a nonmetal (if the cation is monatomic) There are two types of ionic compounds Binary Ionic Compounds: contains the ions of only two elements (NaCl, CaCl 2 ) Polyatomic Ionic Compounds: contain at least one polyatomic ion (CaCO 3, Mg(OH) 2 ) The names DO NOT indicate the ratio of ions present, but the formulas do

11 Names of Charged Particles When electrons are lost, the ion has an overall positive charge and is called a cation Examples: Na +, Ca 2+ When electrons are gained, the ion has an overall negative charge and is called an anion Examples: F -, S 2- The negative ions will attract the positive ions and form a bond All ionic compounds are electrically neutral

12 Ionic Charges Monatomic ions Ions that consist of only one atom Charges often can be determined by using the periodic table Many of the transition metals have more than one charge The charge on the ion is indicated by using a Roman numeral next to the name of the element Cu has a 1+ and a 2+ charge. Cu 1+ is called Copper I, and Cu 2+ is called Copper II A few transition metals have only one charge The names of these do not have to include a Roman numeral Zn, Cd

13 Monatomic Ions Group Atoms that commonly form ions Charge on ions 1 H, Li, Na, K, Rb, Cs 1+ 2 Be, Mg, Ca, Sr, Ba B, Al N, P, As 3-16 O, S, Se, Te 2-17 F, Cl, Br, I 1-

14 Ionic Compounds Writing formulas for binary ionic compounds Compounds composed of two elements are called binary compounds When the formula is written, the charge of the cation must be balanced by the charge of the anion The overall charge of the ion combination must be zero The cation is always written first in the formula

15 Writing Formulas for Ionic Compounds To write the formula for an ionic compound: Write the chemical symbol and overall charge of the cation or polyatomic cation: Na +, Ca 2+, NH 4 + Write the chemical symbol and overall charge of the anion or polyatomic anion: Cl -, O 2-, NO 3 - Add the charges If equal, write the chemical symbols together, e.g. NaCl, CaO, NH 4 NO 3 If not equal, crisscross values of the charges and make them subscripts, e.g. Ca(NO 3 ) 2, CaCl 2

16 Crisscross Method (also called Drop and Swap Na + can combine with S 2- The value of the charge on Na, which is 1, becomes the subscript for S: S The value of the charge on S, which is 2, becomes the subscript for Na: Na 2 The resulting formula is Na 2 S

17 Naming Ionic Compounds Naming binary ionic compounds It is important to know the Stock naming system and the charges on cations before naming ionic compounds The process is the reverse of writing formulas

18 Polyatomic ionic compounds Compounds that contain atoms of three different elements They usually contain a polyatomic ion; must be recognized first to be able to name the compound correctly Tightly bound groups of atoms that behave as a unit and carry a charge Have the suffix ite and ate These ions will be given to you on a sheet; you will not have to memorize them Hydroxide and cyanide are the only common polyatomic ions that end in ide

19 Common Polyatomic Ions Ion Name Ion Name NH + 4 Ammonium NO - 2 Nitrite NO - 3 Nitrate OH - Hydroxide CO 2-3 Carbonate SO 2-4 Sulfate O 2-2 Peroxide C 2 H 3 O - 2 Acetate SO 2-3 Sulfite ClO - 3 Chlorate You will get these on a chart for tests and quizzes!!

20 How Do I Write the Formulas for Polyatomic Ions? Put parentheses around any polyatomic ion and add subscripts to the outside of the parentheses. Never change the subscript of a polyatomic ion (it will change the composition of the ion): Ca(OH) 2, Ca 3 (PO 4 ) 2 Include the subscript inside the parentheses

21 Practice Sodium combines with fluorine Chlorine combines with hydrogen The nitrite ion combines with calcium The ammonium ion combines with nitrogen