Chemistry Chapter 15 Ionic Bonding and Ionic Compounds Remember what ionic bonding is? One atom steals e-, one gives up e- What determines how many e- they give up? Egg valence e- demo

Sec 15.1 Electron Configuration in Ionic Bonding Objectives: Use the periodic table to infer the number of valence electrons in an atom and draw its electron dot structure. Describe the formation of cations from metals and of anions from nonmetals.

Valence Electrons Valence electrons are responsible for chemical bonding and chemical properties among groups. They are the electrons in the highest occupied energy level of an element’s atom. The number of valence electrons is related to the group numbers in the periodic table. Use back row to visualize valence e-

Valence Electrons Electron dot structures are diagrams that show the valence electrons as dots around the symbol.

Write the electron dot structures for each of the following elements. Cl S Al Li

Electron Configurations for Cations Gilbert Lewis said atoms form certain kinds of compounds and ions in order to achieve a noble gas configuration, because they are un- reactive. Octet Rule – in forming compounds and ions, atoms tend to achieve the noble gas electron configuration (8 electrons) Have 8 valence e- ns2 np6 – General Formula

Octet Rule for Cations Metals will lose 1 to 3 electrons to achieve a configuration of the nearest noble gas This makes them a cation (+ charge) Also happens in chemical bonding Before slide: do alkali metals lose or gain e- when becoming ions? How many? 3 legged cat do 3 or 4 examples Neon

Octet Rule for Cations Group 1A elements have 1 valence e- (lose 1 e-) Na. → Na+ + e- Group 2A elements have 2 valence e- (lose 2 e-) Mg: → Mg2+ + 2e- Group 3A elements (only the metals) have 3 valence electrons to lose. → Al3+ + 3e- Using an electron dot structure, show the ionization of Barium: Silver, copper (1), gold (1), mercury (2)

Octet Rule for Cations For transition metals, the charges vary. Iron, for example, may lose two or three electrons. Fe = [Ar]4s23d6 Fe2+ = [Ar] 3d6 Fe3+ = [Ar] 3d5 Write the electron configuration for Zn2+. Zn =[Ar]4s23d10 Zn2+ = [Ar]3d10 Silver, copper (1), gold (1), mercury (2)

Pseudo Noble Gas Configurations Some transition metals don’t have noble gas configurations, but can achieve them by moving an s1 electron to make a full d-subshell. These elements have pseudo noble gas configurations, with d-block electrons in the valence shell. Silver, copper, gold, cadmium, and mercury are examples (elements at the right of the transition metal block)

Write the electron configuration for each of the following: Cu+ Cu = [Ar]4s23d9 Cu+ = [Ar]4s13d9 or [Ar]3d10 Au+ Au = [Xe]6s24f145d9 Au+ = [Xe]6s14f145d9 or [Xe]4f145d10

Octet Rule for Anions Nonmetals will gain 1-3 electrons to achieve the nearest noble gas configuration. The negative charge makes it an anion. Group 15 nonmetals have 5 valence electrons (gain 3 e- to complete the octet) + 3e- → N3- Group 16 nonmetals have 6 valence electrons (gain 2 e- to complete the octet) + 2e- → O2- Group 17 nonmetals have 7 valence electrons (gain 1 e- to complete the octet) + e- → F- What do halogens do to be noble gases? Give 3 or 4 examples Tell about chlorine (p 417 chem & tech) White board races: write e- dot configs and e- configs of ions

Write electron configurations for the following anions. [Ne]3s23p4 + 2e- = [Ne]3s23p6 = [Ar] Cl1- [Ne]3s23p5 + e- = [Ne]3s23p6 = [Ar] P3- [Ne]3s23p3 + 3e- = [Ne]3s23p6 = [Ar] All of these ions have the same noble gas configuration as argon, since they are row three atoms gaining electrons to become stable.

Sec 15.1 Electron Configuration in Ionic Bonding Did We Meet Our Objectives? Use the periodic table to infer the number of valence electrons in an atom and draw its electron dot structure. Describe the formation of cations from metals and of anions from nonmetals.

Sec 15.2 Ionic Bonds Objectives: List the characteristics of an ionic bond. Use the characteristics of ionic compounds to explain the electrical conductivity of ionic compounds when melted and when in aqueous solutions.

Formation of Ionic Compounds Ionic compounds are bonded by the electrostatic attraction of a cation (+) to an anion (-). These bonds are called ionic bonds. The compound is electrically neutral. The total positive charge must equal the total negative charge. Before slide: what is an ionic bond? Link to food science (p418) Become neutral after bonding Na got on eHarmony and found Cl

Potassium and Sulfur Aluminum and Sulfur Use the electron dot structures to predict the formulas of the ionic compounds formed from these elements. Potassium and Sulfur Aluminum and Sulfur HF HCl MgI2 Na2S MgCO3 Write like in book

Write the correct chemical formula for the compounds formed from each pair of ions. K+ and S2- K2S Ca2+ and O2- CaO Na+ and SO32- Na2SO3 Al3+ and SO42- Al2(SO4)3

Properties of Ionic Compounds At room temperature ionic compounds properties include… Repeating Patterns Crystalline solids Strong bonds Minimal repulsion Stable Structure High melting points Get crystals Use ball and sticks Why brittle? Repulsion if moved Waterford & lead poisoning

Properties of Ionic Compounds Coordination number of an ion is the number of ions of opposite charge that surround the ion in a crystal. Na+ and Cl- have coordination numbers of 6 in NaCl crystal. They each have six ions surrounding them. The coordination number depends on the shape of the crystal. The charges and relatives sizes of the ions determines the crystal structure. Chem & enviro (p422) rust and Al2O3 Diamond & graphite Coord #

Properties of Ionic Compounds The internal structures of crystals are determined by a technique called X-ray diffraction crystallography. X-rays pass through a crystal are recorded on film. The pattern on the exposed film shows how ions in the crystal deflect the x-rays. X-ray diffraction like holding a flashlight Before slide: do ions conduct electricity? Minilab (p425) or demo Chemical bonds lab then review 15.1 15.2

Properties of Ionic Compounds Ionic compound crystal structures can break down. This occurs when the ionic compound is melted or dissolved. Properties are different in this state: conduct electricity Ions dissociate and are free to move X-ray diffraction like holding a flashlight Before slide: do ions conduct electricity? Minilab (p425) or demo Chemical bonds lab then review 15.1 15.2

Sec 15.2 Ionic Bonds Did We Meet Our Objectives? List the characteristics of an ionic bond. Use the characteristics of ionic compounds to explain the electrical conductivity of ionic compounds when melted and when in aqueous solutions.

Sec 15.3 Bonding In Metals Objectives: Use the theory of metallic bonds to explain the physical properties of metals. Describe the arrangements of atoms in some common metallic crystal structures.

Metallic Bonds and Metallic Properties Metals consist of closely packed cations They are in a “sea” of valence electrons Metallic bond – consists of the attraction of the free floating valence electrons for the positively charged metal ions. Demo: metal samples Give students tennis palls: they can pass around

Metal Bonds and Properties Metallic bonding explains metallic properties Electricity, ductility, malleability Valence e- move easily and insulate cations from each other. Under pressure, the metal cations can easily slide past one another. Explain malleability, push desks while they pass balls around. Why is it not good to play golf in storm? Explain electricity, have them all throw it at me

Crystalline Structure of Metals Metals are also in crystal form Metal atoms are arranged in very compact and orderly patterns, like tennis balls in a box Have 3 different arrangements Body-centered cubic, face-centered cubic, hexagonal close- packed Body-Centered Cubic Face-Centered Cubic Hexagonal Close-Packed Demo: make these with ball & sticks? Gold: face centered cubic Zinc: hexagonal close packed

Alloys Alloys are mixtures composed of two or more elements, at least one of which is metal. Most metals you encounter aren’t pure elements. Amalgams are alloys that contain mercury. Before slide: what type of metal is …… Bronze: copper, tin brass: copper, zinc Sterling silver: silver, copper Stainless: Fe, Cr, C, Ni Use students to demonstrate bottom part

Alloys Types of alloys Substitutional alloy – The atoms of the components in an alloy are about the same size, they can replace each other in the crystal. Interstitial alloy – The atomic sizes are quite different, and the smaller atoms can fit into the interstices (spaces) between the larger atoms.

Sec 15.3 Bonding In Metals Did We Meet Our Objectives? Use the theory of metallic bonds to explain the physical properties of metals. Describe the arrangements of atoms in some common metallic crystal structures.