Ionic Compounds and Metals Chapter 7 Ionic Compounds and Metals

Section 7.1 Ion formation

Chemical Bonds A chemical bond is the force that holds two atoms together. Can form by the attraction between the positive nucleus of one atom and the negative electrons of another Can form between positive and negative ions

Valence Electrons Electrons in the outermost principal energy level Shown in the electron dot structures Octet rule – atoms will gain, lose or share electrons to obtain 8 valence electrons The valence electrons determine the bonding properties of the atom

Positive Ion Formation A positively charged ion is called a cation. Positive ions are formed when an atom loses one or more valence electrons Metals make positive ions

Negative Ion Formation A negatively charged ion is called an anion. Negative ions are formed when an atom gains one or more electrons in its valence shell. Nonmetals make negative ions.

Ionic bonds and ionic compounds Section 7.2 Ionic bonds and ionic compounds

Formation of an Ionic Bond An ionic bond is the electrostatic force that holds oppositely charged particles together in an ionic compound Compounds that contain ionic bonds are called ionic compounds. Ionic compounds are formed between metals (+ charge) and nonmetals (- charge).

Binary Ionic Compounds Contain a metallic cation and a nonmetallic anion. Formation of Binary Ionic Compounds Electron(s) is/are transferred from metal to nonmetal Metal becomes positive, nonmetal becomes negative Opposite charges attract

Properties of Ionic Compounds Take the structure of a crystal lattice Many units of positive and negative ions stick together in a three-dimensional geometric arrangement Can conduct electricity when dissolved in water (they are electrolytes and break into ions when dissolved in water), but not in solid form Melting point, boiling point and hardness depend upon how strongly the ions are attracted to each other

Names and formulas for ionic compounds Section 7.3 Names and formulas for ionic compounds

Formulas for Ionic Compounds Monatomic ions are one-atom ions Examples: Mg2+ , Br- Oxidation numbers are the charges on ions Note: some elements have multiple oxidation states – you will have a periodic table to tell this Binary ionic compounds are made of two monatomic ions (one positive, one negative)

Formulas for Binary Ionic Compounds Symbol for cation is written first, anion second Subscripts tell the number of atoms of each element What are the following compounds made of? CaF2 1 calcium, 2 fluorine Na2S 2 sodium, 1 sulfur NaCl 1 sodium, 1 chlorine

Naming Binary Ionic Compounds Name the cation first Name the anion second with –ide at the end Examples CaF2  calcium fluoride Na2S  sodium sulfide NaCl  sodium chloride

Try Naming a few more Binary Ionic Compounds K2O potassium oxide Al2S3 aluminum sulfide Na3N sodium nitride

What if the cation has more than one oxidation state? You tell which ion was used by putting a Roman Numeral after the name of the cation Example: CuS We know S was -2 (that’s the only one it makes) If there is only one atom of each element, the Cu must have been +2 So, the name is written as Copper (II) sulfide [the “II” indicates the charge] Make sure, especially with transition elements, that you are checking the oxidation states

Writing Formulas for Binary Ionic Compounds Look up the charges for each element For a compound to form, the total charge must balance out to zero (positive charges must equal negative charges) Example: Sodium bromide Na is +1, Br is -1 Only need one of each to balance Formula is NaBr

Try writing some more formulas Binary Ionic Compounds Potassium Iodide KI Aluminum bromide AlBr3 Magnesium chloride MgCl2 Cesium nitride Cs3N

Formulas for Polyatomic Ionic Compounds Polyatomic ions are ions that are made up of more than one atom You will have a chart for these and do not have to memorize them. Examples: SO42- = sulfate CN- = cyanide NH4+ = ammonium

Naming Polyatomic Ionic Compounds Name the cation first, anion second Name the polyatomic as is – don’t change its name at all Examples: Ca3(PO4)2 calcium phosphate Mg(CN)2 magnesium cyanide NH4Cl ammonium chloride

Now you try naming Polyatomic Ionic Compounds NaNO3 sodium nitrate Ca(ClO3)2 calcium chlorate Al2(CO3)3 aluminum carbonate

Writing formulas for Polyatomic Ionic Compounds Same as binary ionic compounds EXCEPT you may not change anything in the polyatomic ion formula Put them in a “bubble” and put subscripts outside that bubble Example: Calcium Nitrate Ions are Ca2+ and NO3- Formula will be Ca(NO3)2

Now you try writing formulas for Polyatomic Ionic Compounds Sodium hydroxide NaOH Copper (II) nitrate Cu(NO3)2 Silver chromate Ag2CrO4

Metallic bonds and the properties of metals Section 7.4 Metallic bonds and the properties of metals

Metallic Bonds The electron sea model proposes that all the metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons Since the electrons are free to move, they are called delocalized electrons A metallic bond is the attraction of a metallic cation for delocalized electrons

Properties of Metals (revisited) Moderately high melting points High boiling points Malleable, ductile, durable Conduct heat and electricity well Transition metals are harder/stronger than alkali metals because the transition metals have more delocalized electrons