Chapter 7 An ion is an atom that has gained or lost electrons from the valence shell Valence electrons are the electrons contained in the highest occupied energy level These electrons will mostly determine the chemical properties of the element ID: 642236
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Slide1
Ionic and Metallic Bonding
Chapter 7Slide2
An ion
is an atom that has gained or lost electrons from the valence shell.
Valence electrons are the electrons contained in the highest occupied energy levelThese electrons will mostly determine the chemical properties of the elementFor representative elements, group # = # valence electronsException is Helium with 2 valence e-
7.1 IonsSlide3
Diagrams that show the number of valence electrons
Also called Lewis Dot Diagrams
Electron Dot StructuresSlide4
Gilbert Lewis recognized that Noble Gases are
inert
.These elements have a full s and p sublevel and with the exception of Helium have 8 valence e-.He realized that atoms will bond in order to achieve noble gas e- configuration.Atoms of metals tend to lose their valence e-, leaving a complete octet in the next lowest energy level. Atoms of nonmetals tend to gain e- or to share e- with one another to complete an octet.
The Octet Rule
Magic # = 8Slide5
An atom’s loss of valence e- produces a
cation
, or (+) charged ion.Metals have relatively low ionization energy. It requires less energy to remove 1,2,3, or 4 valence electrons.Metals have relatively low electronegativity and are not likely to gain electrons.Metals will typically lose all valence electrons and have a charge equal to the number of electrons lost.
Formation of
CationsSlide6
Atoms will lose valence e- in order to achieve the electron configuration of the nearest noble gas.
E- Configuration of
cations
e- configuration for NeSlide7
Transition metals do not always form Noble gas electron configuration when forming
cations
.Because of the partially filled d sublevel, they form pseudo noble gas configurationsSilver will form a +1 ionCopper can form +1 or +2
Transition MetalsSlide8
Once electrons are removed from a neutral atom a positive charge will exist.
For
cations, the name of the metal is the same as the name of the cation.Al is called aluminum.Al+3 is still called aluminum.
Naming
CationsSlide9
The gain of negatively charged electrons by a neutral atom produces an anion.
Most nonmetals have more than 4 e- in the valence shell.
They will gain e- in order to achieve the noble gas configuration of the nearest noble gas.Formation of AnionsSlide10
When atoms from group 7A gain e-, they will have a charge of -1. These anions are called
halide
ions.Once a nonmetal gains electrons, the name of the ion will be different from the name of the neutral ion.For monatomic anions, drop the ending and add –ide.Ex: Oxide, Phosphide, Sulfide, Fluoride, Chloride
Naming AnionsSlide11
Compounds composed of cations
and anions are called
ionic compounds.Ionic compounds are typically neutral.The electrostatic forces that hold ionic compounds together are called ionic bonds.Just like when forming ions, ionic compounds consist of
cations
and anions seeking a complete octet.
7.2 Ionic BondsSlide12
A chemical formula
shows the kinds and numbers of atomic in the smallest representative unit of a substance.
Ionic compounds are not typically found as just one unit. Typically a regular, repeating pattern of ionic bonds will exist.In other words, a compound like NaCl will be connected to several other NaCl units.A
formula unit
is the lowest whole-number ratio of ions in an ionic compound.
Formula UnitSlide13
Write the formula for both the
cation
and the anion.Eliminate the (+) and (-) charges.“Drop and drag” the numbers remaining as subscripts for the formula unit.No charges will remain in the final formula.Predicting Formula UnitsSlide14
Atoms
Combining
Ion FormulasFormula
Name
Sodium and Sulfur
Barium and Oxygen
Calcium and Phosphorus
Potassium and Nitrogen
Aluminum and Oxygen
Lithium
and Iodine
Practice Formula Writing and NamingSlide15
Most ionic compounds are crystalline solids at room temperature.
Arranged in regular, repeating, 3-D patterns
Structure is related to coordination number (number of oppositely charged ions surrounding an ion.)See some examples here.Ionic compounds have high melting points.Ionic compounds conduct an electric current when melted or dissolved in water.
Properties of Ionic CompoundsSlide16
Metals are made up of closely packed
cations
rather than neutral atoms.The valence electrons of metals can be modeled as a sea of electrons.Valence e- are mobile and can drift freelyMetals are ductile and malleableMetals conduct electricityMetal atoms are arranged in very compact and orderly patterns.Check out
this cool
Nova Explanation of metals!
7.3 Bonding in MetalsSlide17
Alloys are mixtures composed of two or more elements, at least one of which is a metal.
Alloys are important because their properties are often superior to those of their component elements.
Sterling silver: silver and copperBronze: copper and tinSteel: iron, carbon, boron, chromium, manganese, molybdenum, nickel, tungsten, and vanadium
Alloys