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The attraction of opposites
What Is an Ionic Bond?An ionic bond is the attraction of
two oppositely charged ions. These ions combine and the
opposite charges cancel each other out like the electrons and protons of an atom.
Combining the ions of different elements creates new matter that is useful to the world today.
For example, when a sodium atom bonds with a chlorine ion, they form sodium chloride which is table salt.
Electron Transfer
When an atom has less than eight valence electrons it is not chemically stable and must get chemically stable,It will lose electrons or gain electrons to fill its last energy level and therefore become chemically stable.
Ionic Bonding
Metals will always lose electrons to become chemically stable
Metals will form positive ions
Non metals will always gain electrons to become chemically stable
Nonmetals will always form negative ions
Example Of An Ionic Bond
When a sodium atom and a chlorine atom combine, sodium’s one valence electron gets transferred or moved to the chlorine atom. Both atoms are now ions; – sodium is positive and – chlorine is negative. – The ions attract each other and bond.
These two form Sodium Chloride, which is table salt.
Diagram: Na + Cl
Sodium’s 1 valence electron is transferred to Chlorine.
Result: Na + Cl NaCl
Chlorine is stable (8 valence electrons).
Sodium is now stable too (8 valence electrons).
Forming Ionic BondsThings to remember!
An ionic bond is the attraction between two oppositely charged ions.
Oppositely charged ions attract each other.
Ionic bonds are formed when electrons are taken and not shared.
Pictures of Forming Ionic Bonds
The ions attract each other. Therefore, they bond.
Ionic bonding forms compounds
Ionic bonding doesn’t form molecules
The oppositely charged ions are attracted to each other – forming very strong bonds!!
Crystal Shape
Every ion in an ionic bond is attracted to ions near it that have an opposite charge.
Because of this, all the ions attract many ions.
Therefore, they create a shape.
This shape is 3-D and is called the crystal shape.
Characteristic of ionic bonds:
Crystal ShapeIonic solids are generally high melting pointsIonic solids are hard and brittle Ionic solids conduct electricity only when they are dissolved in water
Electrical Conductivity
When ionic compounds are dissolved in water, they conduct electricity.When they are solid, they don’t conduct.The ions are tightly bound together and have no room to move or let the electricity flow through.When dissolved, the ions move more freely; therefore, electricity can flow through them.
High Melting Points
Ionic Bonds are very strong.
It takes a lot of heat (energy) to make the particles have enough energy to overcome the attractive forces.
Ionic bonds are so strong that all ionic bonds are solids at room temperature.
Elements Which Form This Bond
Metal + Nonmetal = Ionic Bond
Common Ions Which Form This Bond
Lithium
Sodium
Potassium
Calcium
Magnesium
Aluminum
Oxide
Fluoride
Chloride
Iodide
Sulfide
Writing Chemical formulas for ionic compounds.
• Example:
• Mg Br
7 valence electrons2 valence electrons
The point of ionic bonding is giving the electron so that Br can become chemically stable, for it to become chemically stable, the valence electron has to be 8.
BrThe reason you have to double the Br is because you cant have more than 8 valence electrons in one element
The Chemical formula for this compound is MgBr2. This translates to one magnesium and two Bromide.
Pictures Of Atomic Bonds
Ionic Bond
Covalent Bond
Polyatomic IonsA Polyatomic ion is an electrically charged collection of more than one atom. Polyatomic ions usually have a charge because the collection of atoms has either gained or lost an electron.
Each polyatomic ion has an overall positive or negative charge. If a polyatomic ion combines with an ion of an opposite charge, an ionic compound forms.
Example of A Polyatomic Ion
Carbonate ion (CO32-), made of 1 carbon atom & 3 oxygen atoms.
Combines with Calcium ion (Ca2+).
Makes Calcium Carbonate (CaCO3)
Did You Understand?
What properties do ionic compounds have?
Why are ions in ionic compounds attracted to each other?
What are polyatomic ions?
What is the process of Ionic Bonding?
Summary: What is an Ionic Bond?
Covalent Bonding
Covalent BondingCovalent Bond: – a bond formed by the sharing of
electrons between atoms. (does NOT form charges)
– Made up of nonmetals
Molecule: a neutral group of atoms joined together by covalent bonds. (Compounds formed with ionic bonds do NOT have molecules) Molecular Formula: chemical formula for a molecular compound. It shows how many atoms of each element a molecule contains.
Covalent BondingExamples: ascorbic acid (vitamin C): C6H8O6
C_____, H_____, O_____,
trinitrotoluene (TNT): C7H5N3O6
C_____, H_____, N_____, O_____,
6 8 6
7 5 3 6
Molecular Nomenclature
Prefix System (binary compounds)
1. Less electronegative atom comes first.
2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element.
3. Change the ending of the second element to -ide.
most
PREFIXmono-di-tri-tetra-penta-hexa-hepta-octa-nona-deca-
NUMBER123456789
10
Molecular Nomenclature
P2O5 =CO2 =
CO =
N2O =
diphosphorus pentoxide
carbon dioxide
carbon monoxide
dinitrogen monoxide
Naming Covalent Binary Compounds
Naming Covalent Binary Compounds
PCl5N2H4
Cl2O7
IO2
phosphorous pentachloride = dinitrogen tetrahydride
=dichlorine heptaoxide =iodine dioxide =
Lewis Structures
Electron Dot Diagrams–show valence e- as dots–distribute dots like arrows in an orbital diagram
–EX: oxygen
O
X
Lewis Structures
Octet Rule–Most atoms form bonds in order to obtain 8 valence e-
–Full energy level stability ~ Noble Gases
Ne
Diatomic Molecules• Diatomic Molecule: a molecule
consisting of two atoms.• Diatomic molecules in nature:
H2, N2, O2, F2, Cl2, Br2, I2
#s of Covalent Bonds
Cl Cl
O O
N N
Single Bond: 2 e- shared
Double Bond: 4 e- shared
Triple Bond: 6 e- shared
Polyatomic Ions and covalent bonding “CHLORATE”
O
Cl O
O
Chlorine has 7 valence e-
Each oxygen has 6 valence e-
When ClO3 comes together they form 3 single covalent bonds
One additional electron completes chlorine with a full valence shell, making this a covalently bonded group with an ionic charge of -1
-1
Polarity
Bond Polarity
Most bonds are a blend of ionic and covalent characteristics.
Difference in electronegativity determines bond type.
E difference: 0.0-0.4
E difference: 0.4-1.7
E difference: >1.7
Bond Polarity
Electronegativity–Attraction an atom has for a shared
pair of electrons.–higher e-neg atom -
–lower e-neg atom +
Bond Polarity
Electronegativity Trend – Increases up and to the right.
Table of Electronegativity
Nonpolar Covalent Bond–e- are shared equally–symmetrical e- density–usually identical atoms
Bond Polarity
+ -
Bond Polarity
Polar Covalent Bond–e- are shared unequally–asymmetrical e- density– results in partial charges (dipole)
• Nonpolar– e- shared equally
• Polar– e- shared
unequally
• Ionic– e- transferred
Bond Polarity
E difference: >1.7
E difference: 0.4-1.7
E difference: 0.0-0.4
+ -
+
Bond Polarity
Nonpolar Covalent – equally shared e-
Polar Covalent - partial charges, e- shared unequally
Polar MoleculeOne end of the molecule is slightly negative and the other end is slightly positive
Caused by the presence of a polar bond in the molecule. (structure is not symmetrical)
A molecule that has two poles is called a dipolar molecule, or dipole.
+
FH
Self Test
Is CO2 a covalent or ionic compound?
What is CO2 ’s name?What is the electronegativity difference between C and O?
Does CO2 have polar bonds?
Is CO2 a polar molecule overall?
. .O. .
C: :O
Bonding Summary
Ionic Covalent
Octet achieved by:
Transfer of electrons (forming + & - ions)
Sharing electrons
Made of:Metal cation (+) & Nonmetal
anion (-)Nonmetals (above metalloid
line) (no charges)
Characteristics: Brittle Soft and Squishy
Structure:Arranged in alternating
+ & - ions (crystal lattice)Individual molecules
Representative Particle:
Formula Unit: (lowest whole number ratio of
atoms)
Molecule: (group of joined atoms)
Bonding Summary
Ionic Covalent
Physical State: Solid Solid, Liquid, Gas
Melting Point: High Low
Electrical Conductivity:
Yes, when dissolved in water or melted
No
Quiz - answer the following on a sheet of paper
1. The following ball-and-stick molecular model is a representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple (red = O, gray = C, blue = N, ivory = H):
(a) What is the molecular formula of thalidomide?
2. Above is a ball-and-stick molecular model representation of acetaminophen, the active ingredient in such over-the-counter headache remedies as Tylenol (red = O, gray = C, blue = N, ivory = H):(a) What is the molecular formula of acetaminophen?