ionic compounds and metals chemistry unit 6 main ideas ions are formed when atoms gain or lose...
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Ionic Compounds and
MetalsChemistry Unit 6
Main IdeasIons are formed when atoms gain or lose valence electrons to achieve a stable octet electron configuration.
Oppositely charged ion attract each other, forming electrically neutral ionic compounds.
In written names and formulas for ionic compounds, the cation appears first, followed by the anion.
Metals form crystal lattices and can be modeled as cations surrounded by a “sea’” of freely moving valence electrons.
Ion FormationIons are formed when atoms gain
or lose valence electrons to achieve a stable octet electron configuration.
Goals and Objectives:
Define a chemical bond.
Describe the formation of positive and negative ions.
Relate ion formation to electron configuration.
Valence Electrons and Chemical
BondsChemical Bond – is a force that holds two atoms together.
They can form between the positive nucleus of one atom and the negative valence electrons of another atom or between two oppositely charged ions.
Valence Electrons and Chemical
BondsAtom’s try to form the octet – the stable arrangement of eight valence electrons in the outer energy level – by gaining or losing valence electrons.
The transfer of valence electrons between two atoms is based on the ionization energy and electron affinity of the two atoms.
Noble gases- high ionization energy + low electron affinity = little chemical reactivity.
Positive Ion Formation
Cation – positively charged ionExample:
Sodium atom:1s2 2s2p6 3s1
Sodium ion:1s2 2s2 p6 = neon
Positive Ion Formation
Metal atoms are reactive because they lose valence electrons easily.
Group 1: commonly form +1 ionsGroup 2: commonly form +2 ionsGroup 13: sometimes +3 ions
Positive Ion Formation
Transition metal ions have an outer shell of s2
They will lose their s electrons and occasionally a d electron.Typically form +2 or +3 ions but can form greater than +3 ions
Positive Ion Formation
Other relatively stable electron arrangements are referred to as pseudo-noble gas configurations.
Groups 11-14 will lose electrons to form full outer shells: s, p, and d.
Negative Ion Formation
An anion is a negatively charged ion. (Add “-ide” to the end of the root atom name.)
Nonmetals easily gain electrons.Example:
Chlorine atom:1s2 2s2p6 3s2p5
Chlorine ion:1s2 2s2p6 3s2p6 = Argon
Negative Ion Formation
Nonmetal ions gain the number of electrons required to fill an octet.
Some nonmetals can gain or lose electrons to complete an octet.
Phosphorus can gain 3 or lose 5Group 15 usually gains 3 electronsGroup 16 usually gains 2 electronsGroup 17 usually gains 1 electron
Practice Problems
CALM 6:1
Ionic Bonds and Ionic Compounds
Ionic Bonds and Ionic Compounds
Oppositely charged ions attract each other, forming electrically neutral ionic compounds.
Goals and Objectives:
Describe the formation of ionic bonds and the structure of ionic compounds.
Generalize about the strength of ionic bonds based on the physical properties of ionic compounds.
Categorize ionic bond formation as exothermic or endothermic.
Ionic Bond
Ionic Bond is the electrostatic force that holds oppositely charged particles together.
Ionic Compound is a compound that contains an ionic bond.
Ionic bonds between metals and oxygen are called oxides.Most other ionic compounds are considered salts.
Binary Ionic Compound
Binary Ionic compound is an ionic compound that contains two different elements.
One metallic cation and a nonmetallic anion.Examples: NaCl, MgO, KBr, LiF
Ionic Bond Formation
Electrons gained and lost in each element must be equal. (conservation of electrons)
Calcium and Fluorine
Aluminum and Oxygen
Sodium and Chlorine
Properties of Ionic Compounds
Compounds are organized such that a pattern repeats to balance attraction and repulsion
Total charge of a compound is neutral
Often highly organized
Example: NaCl crystal
Crystal Lattice
A crystal lattice is a three dimensional geometric arrangement of particles.
Each negative ion is surrounded by a positive ion which results in strong attractions between ions.Size and shape are dependent on relative numbers of ions.
Crystal LatticePhysical Properties:
Characteristics of bond strength – ionic bonds are relatively strong and take a large amount of energy to break.
Melting point – highBoiling point – highHardness of material is high: rigid and brittle solids.
Properties of Ionic Compounds
Crystal LatticeCharacteristics of the compound:
Conducts electricity, conditionallyIons in solid state ionic compounds are locked in place and they do not have free electrons in order to conduct electricity.Ionic compounds that are melted or dissolved in aqueous solutions have ions that are free to move and therefore do conduct electricity
Electrolyte – an ionic compound that conducts electricity in an aqueous solution.
Energy and the Ionic Bond
Formation of ionic compounds forms a more stable system and therefore reduces the energy required to sustain it.
Since the creating of bonds lowers energy, energy is released in the process. The creation of bonds is said to be Exothermic.
Exothermic – energy is released during a chemical reaction.
Energy and the Ionic Bond
Breaking of ionic compounds reduces the stability of a system and therefore increases the energy required to sustain it .
Since the creating of bonds lowers energy, the breaking of bonds increases energy and therefore it is required for the process.
Endothermic – energy is absorbed during a chemical reaction.
Lattice EnergyLattice energy is the energy required to separate 1 mole of the ions of an ionic compound.
higher the lattice energy the stronger the bond strength.Directly related to the size of the ions bonded.
smaller ions form compounds more closely because attraction increases with decreased distance.
Also affected by charge of ionsHigher ion charge typically has higher lattice energy.
Lattice Energy
Practice ProblemsCALM 6:2
Names and Formulas for Ionic
Compounds
Names and Formulas for Ionic
CompoundsIn written names and formulas for ionic compounds, the cation appears first, followed by the anion.
Goals and Objectives:
Relate a formula unit of an ionic compound to its composition.
Write formulas for ionic compounds and oxyanions.
Apply naming conventions to ionic compounds and oxyanions.
Formulas for Ionic Compounds
A standardized system for naming compounds was developed for much the same reason as the SI unit system. This serves as a universal naming system for communication among the science community.
Formula UnitA formula unit is the chemical formula for an ionic compound and represents the simplest ratio of ions.
MgCl2 not Mg4Cl8
A monoatomic ion is a one atom ion.
Oxidation number
Oxidation number (oxidation state) the charge of a monatomic ion.
Formulas for Ionic Compounds
The symbol for the cation is written first with the anion second.
Subscripts represent the number of atoms of each element in a compound.
The total charge must equal zero in an ionic compound.
Polyatomic IonsPolyatomic ions are made up of more than one atom.
Formulas for polyatomic ionic compounds
Charge applies to the entire group of atoms.Parentheses are used if more than one polyatomic ion is needed to balance a compound.
Do not change subscripts within the ion groupExample (NH4)O
Polyatomic Ions
Oxyanion
An oxyanion is a polyatomic negative ion composed of an element, usually a nonmetal, bonded to one or more oxygen.
Oxyanion Naming Rules
Names for Ions and Ionic
Compounds1. Name the cation followed by the
anion.
2. For monatomic cations, use the element name.
3. For monatomic anions, use the root of the element with the suffix –ide.
Names for Ions and Ionic
Compounds4. Multiple oxidation states are represented by a Roman numeral in paranthesis after the cation.a) This applies to transition metals with
more than one oxidation state and not the Group 1 and 2 cations.
b) Example: FeO is Iron (II) oxide; Fe2O3 Iron (III) oxide.
5. With a polyatomic ion, name the cation followed by the name of the polyatomic ion.a) Example: NaOH is sodium
hydroxide.
Problem Solving
Practice Problems
CALM 6:3
Metallic Bonds and the
Properties of Metals
Metallic Bonds and the
Properties of MetalsMetals form crystal lattices and can be
modeled as cations surrounded by a “sea” of freely moving valence electrons.
Goals and Objectives:
Describe a metallic bond.
Relate the electron sea model to the physical properties of metals.
Define alloys, and categorize them into two basic types.
Metals
Metals are not ionic but share several properties with ionic compounds.
Metals also form lattices in the solid state, where 8 to 12 other atoms closely surround each metal atom.
Within the crowded lattice, the outer energy levels of metal atoms overlap.
Electron Sea Model
The electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electron.
The electrons are free to move around and are referred to as delocalized electrons, forming a metallic cation.
Metallic Bonds
A metallic bond is the attraction of an metallic cation for delocalized electrons
Properties of Metals
Boiling points are much more extreme than melting points because of the energy required to separate atoms from the groups of cations and electrons.
Properties of Metals
Metals are malleable because they can be hammered into sheets.
Metals are ductile because they can be drawn into wires.
Properties of Metals
Mobile electrons around cations make metals good conductors of electricity and heat.
As the number of delocalized electrons increases, so does hardness and strength.
Metal Alloys
An alloy is a mixture of elements that has metallic properties.
The properties of alloys differ from the elements they contain.
Metal Alloys
Metal Alloys
Substitutional alloys are formed when some atoms in the original metallic solid are replaced by other metals of similar atomic structure.
Interstitial alloys are formed when small holes in a metallic crystal are filled with smaller atoms.
Practice Problems
CALM 6:4
Accumulating Content
How does the electron configuration of a neutral element compare to that of its ion configuration?
Accumulating Content
How does energy and stability relate to ion formation and bond formation?
Accumulating Content
What are some physical and chemical properties of metals that are caused by the way they ionize or bond?
Study GuideKey Concepts
Key ConceptsA chemical bond is the force that holds two atoms together.
Some atoms form ions to gain stability. This stable configuration involves a complete outer energy level, usually consisting of eight valence electrons.
Ions are formed by the loss or gain of valence electrons.
Key Concepts
The number of protons remains unchanged during ion formation.
Ionic compounds contain ionic bonds formed by the attraction of oppositely charged ions.
Ions in an ionic compound are arranged in a repeating pattern known as a crystal lattice
Key Concepts
Ionic compound properties are related to ionic bond strength.
Ionic compounds are electrolytes; they conduct an electric current in the liquid phase and in aqueous solution.
Lattice energy is the energy needed to remove 1 mol of ions from its crystal lattice.
Key Concepts
A formula unit gives the ratio of cations to anions in the ionic compound.
A monatomic ion is formed from one atom. The charge of a monatomic ion is its oxidation number.
Roman numerals indicate the oxidation number of cations having multiple possible oxidation states.
Key Concepts
Polyatomic ions consist of more than one atom and act as a single unit.
To indicate more than one polyatomic ion in a chemical formula, place parentheses around the polyatomic ion and use a subscript.
A metallic bond forms when metal cations attract freely moving, delocalized valence electrons.
Key Concepts
In the electron sea model, electrons move through the metallic crystal and are not held by any particular atom.
The electron sea model explains the physical properties of metallic solids.
Metal alloys are formed when a metal is mixed with one or more other elements.
QuestionsCations form when atoms _______
electrons.
A.gain
B. lose
C. charge
D.delocalize
QuestionsWhat is the repeating pattern of atoms in
an ionic solid called?
A.crystal lattice
B. ionic lattice
C. energy lattice
D.ionic bonding
QuestionsGive the name of the following: NaClO4
A.sodium hypochlorite
B. sodium chlorite
C. sodium chlorate
D.sodium perchlorate
QuestionsAs the distance between ions in an ionic
bond is shortened,
A. the energy to break the bond decreases.
B. the electrostatic attraction decreases.
C. the electrostatic attraction increases.
D.the ionic bond changes to a metallic bond.
QuestionsAn alloy is what type of substance?
A.heterogeneous mixture
B. compound
C. mixture of elements
D.element
QuestionsWhich is NOT true about metallic solids?
A.Metals are shiny.
B. Metals are good conductors of heat and electricity.
C. Metals are ductile.
D.Metals have relatively low boiling points.
QuestionsElectrons in an atom’s outer most energy
level are referred to as what?
A. ions
B. cations
C. valence electrons
D.noble-gas electrons
QuestionsWhat is the oxidation state of copper in
Cu(II)Cl2?
A.1+
B. 2+
C. 2–
D.unable to determine
QuestionsWhich elements naturally occur with a full
octet of valence electrons?
A.alkali metals
B. alkali earth metals
C. halogens
D.noble gases
QuestionsHow many electrons are in a full octet?
A.10
B. 8
C. 6
D.4
The End
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