Ionic Bonding and Ionic Compounds Chapter 5 Ridgewood High School

Valence Electrons Valence electrons are the electrons in the highest occupied energy level of an element’s atoms. Q. How many valence electrons does group 2a have? A. Two electrons in the out valence electron shell.

Valence Electrons Potassium after it loses one electron has the same electron configuration as chlorine after it gains one. Both are the same as that of the noble gas argon. [Ar] = 1s 2 2s 2 2p 6 3s 2 3p 6 The atoms of many elements become stable by achieving the electron configuration of a noble gas. The electrons in the outer energy level are known as valence electrons.

Electron Dot Structures Valence electrons are illustrated around the symbol of the atom. (also called Lewis Dot Structures)

Octet Rule Understanding that noble gases are un- reactive in chemical reactions can explain why atoms form certain kinds of ions and molecules. In forming compounds, atoms tend to achieve the electron configuration of a noble gas. ns 2 np 6

Ions With Noble Gas Notation

Loss of Valence Electrons Na.  Na + + e - Sodium atom (electrically neutral) with ionization energy yields a sodium ion and an electron. Mg:  Mg e - Magnesium atom (electrically neutral) with ionization energy for removal of two electrons yields a magnesium ion and two electrons.

Electron Configurations and Noble Gases Depending on whether your adding or taking away electrons, you want to have 8 electrons in your outer shell This therefore creates a noble gas notation. CATION- Mg:  Mg e - What is this elements noble gas?. A. Neon ANION- :Cl: + e -  Cl - ‘ ‘ What is this elements noble gas? A. Argon

How Many Valence Electrons Do the following atoms have? Potassium Magnesium Carbon Oxygen K = 1 Mg = 2 C = 4 O = 6

Write the Electron Dot Structure for the following atoms Potassium Magnesium Carbon Oxygen

How many electron will each element gain or lose in forming an ion? Calcium Fluorine Aluminum Oxygen Calcium- lose 2 Fluorine- gain 1 Aluminum- lose 3 Oxygen- gain 2

Section 5.2: Ionic Bonds Ionic Bond is a bond created from the forces of attraction that bind oppositely charged ions. For example a metal (positively charged) and a nonmetal (negatively charged)

Question: Ionic Bonding Use electron dot structures to predict the formulas of the ionic compounds formed from these elements. Potassium and oxygen Sodium and nitrogen One electron from each potassium bonds to the lone electrons on the Oxygen. Every 2 electrons involved in a bond can be drawn as a straight line.

Properties of Ionic room temperature- crystalline solids They are repeating 3-D patterns Coordination number: an ion is the number of ions of opposite charge that surround the ion in a crystal. Pg 423 figure 15.9 The internal structures of crystals are determined by a technique called x- ray diffraction crystallography.

Write the correct chemical formula for the compounds formed from each pair of ions. K +, S 2- Ca 2+, O 2- Na +, SO 4 2- Al 3+, PO 4 3- K 2 S CaO Na 2 SO 4 AlPO 4

Write the formulas for each compound. Potassium nitrate Barium chloride Magnesium sulfate Lithium oxide Ammonium carbonate Calcium phosphate KNO 3 BaCl 2 MgSO 4 Li 2 O (NH 4 ) 2 CO 3 Ca 3 (PO 4 ) 2

5.3 Bonding Metals Metals: composed of closely packed cations rather than neutral atoms. The cations are surrounded by mobile valence electrons which can drift freely in the metal.

Metallic Bonds Metallic Bonds: these bonds consist of the attraction of the free-floating valence electrons for the positively charged metal ions. A metal rod can be forced through a narrow opening in a “die” to produce wire. As this occurs, the metal changes shape but remains in one piece.

Metallic Properties Strong conductors of electrical current Malleable: easily bendable Ductile: metal can be drawn into wire Both malleability and ductility of metals can explain the mobility of valence electrons Malleable Ductile

Crystalline Structure of Metals Metals that contain one kind of atom are in simple forms of crystalline solids Metals are arranged in very compact and orderly patterns.

Three Arrangements of Crystalline Solids Body-centered Face-centered

Alloys Alloys: are mixtures composed of two or more elements, at least one of which is a metal. Prepared by melting a mixture of the ingredients and then cooling the mixture. Ex: Brass is a mixture of copper and zinc

Properties of Alloys Generally superior to their component elements Sterling silver (silver and copper) is harder and more durable then pure silver, but still soft. Bronz (copper and tin) is harder then copper but more easily cast.

Ions Atoms or groups of atoms that have a positive or negative charge. An ION forms when an atom or group of atoms gains or loses electrons. Metallic atoms tend to loose electrons and nonmetal atoms tend to gain electrons

Cation vs. Anion Cation: is any atom or group of atoms that has a positive charge. Ex: Na (sodium) has 11p + and 11e -, but because it is a metal it tends to lose electrons. It is typically Na + in nature. Anion: is any atom or group of atoms that has a negative charge. Ex: Cl (chlorine) has 17p + and 17e -, but because it is a nonmetal it tends to gain electrons. It is typically Cl - in nature. The ending changes for anions ~ide. Chloride= Cl -

Questions????? Give the name and symbol of the ion formed when: 1. a sulfur atom gains two electrons. 2. an aluminum atom loses three electrons. 3. a calcium atom loses two electron.

Questions???? How many electrons are lost or gained in forming each ion? 1. Ba As Cu 2+

Ionic Compound Compounds composed of cations and anions are typically referred to as ionic compounds. Typically found as solids They have high melting points They are formed from a metal and nonmetal

Review Questions???? What does the presence of an –ide ending on the name of an ion tell you about that ion? A. That the atom or groups of atoms are negatively charged, or an anion.

Chemical Formula vs. Molecular Formula Chemical Formula: shows the kinds and numbers of atoms in the smallest representative unit of the substance. Ex: O = Oxygen O 2 = “oh 2” Molecular Formula: shows the kinds and numbers of atoms present in a molecule of a compound. Ex: H 2 O= “h 2 oh”

Formula Unit Formula Unit: is the lowest whole number ratio of ions in the compound. Ex: the lowest whole number ratio of sodium chloride is 1:1 (1Na + and 1Cl - ), therefore the formula unit for sodium chloride is NaCl.

Formula Unit Ex: Magnesium Chloride has Mg cations and Cl anions. Mg 2+ and Cl - they then have to switch their charges and make them subscripts Mg 2+ Cl -  MgCl 2 The number 1 is not written in

Why Do Charges Change Places? A Chloride anion has a charge of –1 Magnesium cation has a charge of +2 So to make the compound electrically neutral there must be two chlorides for every one magnesium.

Question???? What is the ratio of aluminum ions to chloride ions in aluminum chloride and write out the compound? Al +3 Cl -  A. 1:3 AlCl 3

Question???? What is the charge on the Iodide Ion?  A. I -

Names of Common Metal Ions Copper (I), (II) Iron (II), (III) Mercury (I), (II) Lead (II), (IV) Tin (II), (IV) Chromium (II), (III) Manganese (II), (III) Cobalt (II), (III)

Question???? What is the charge of the ion typically formed by each element? a.sulfure b. lead (4 electrons lost) c. strontium d. argon e. bromine f. copper,(1 electron lost)  Answer:  a. 2- b. 4+  c. 2+ d. no ion formed  e. 1- f. 1+