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Chemical BondingChapter 13
To Bond or Not to Bond
But instead there is an attraction.
Atoms bond by gaining, losing or sharing electrons.
Common Chemical Formulas
• C6H12O6 Glucose
• C6H8O6 Vitamin C
• C6H8O7 Citric Acid
• C2H5OH Ethyl Alcohol
Definitions
• Compound: A substance made up of atoms of 2 or more different elements joined by Chemical Bonds.
• Molecule: The smallest unit of a substance that keeps all of the physical and chemical properties of that substance.
• Rule of 8 (Octet):Elements gain or lose electrons to become like the closest Noble gas.
More Definitions
• Ion: A charged particle that forms when an atom or group of atoms gains or loses one or more electrons.
• Anion: A negatively charged particle
• Cations: A positively charged particle
Remember!!
8 valence electrons in the outer shell is considered complete except for Helium which has a complete outer shell of 2.
The Goal of Bonding
Create Neutrally Charged Particles!
Valence Electrons are the Key
Element Types
• Metals usually give up electrons.– 1 to 2, rarely 3.– Atoms become
ElectroPositive (Cations)
• Non Metals gain electrons easily.– Atoms become
Electronegative (Anions)
Element types
• Metalloids and Noble gases are least likely to bond.
Types of Bonding
• Ionic• Covalent• Metallic
Ionic Compounds
• Salts• Created when metal
ions and non Metal ions bond.
• They have a strong attraction!
Energy is needed to gain or lose electrons
Only small amounts of energy is needed to take an electron from
a metal!
When an atom gains electrons they give off energy as well.
The easier an atom gains electrons the more energy they
give off.
Magnesium
• 2 Valence Electrons• Neutral
Magnesium Ion (Mg2+)
• Loses 2 electrons• Becomes a Positive
Ion (Cation)
Oxygen
• 6 Valence electrons• Neutral
Oxygen Ion (O2-)
• Gains 2 electrons• Becomes a negative
ion (anion)• ‘ide’ is added to the
end of an ion that gains electrons.
• Oxide
Magnesium Oxide
• MgO
Sometimes it takes more than one of each atom to make an
Ionic Compound
Magnesium Chloride MgCl2
+
Remember that the total electrons lost must equal the total
electrons gained.
Al3O2
Aluminum Oxide
• Aluminum has 3 valence electrons
• Oxygen needs 2 to complete the Octet.
Aluminum Oxide
OR
Aluminum Oxide
Al3+
Al3+
O2-
O2-
O2-
Properties of Ionic Compounds
Most have similar characteristics
Remember
Ionic Compounds are created because of a strong attraction
between Metals and Non Metals
Form Crystals
• The salt you eat is a crystal!
Brittle
• Can be ‘Cleaved’– Split
• When hit (pressure) the layers shift and line up making a crack.
High Boiling and Melting Point
• Sodium Chloride melts at 801oC
• Boils at 1465oC or 2669oF
• Salt water Boils at a higher temperature than regular water.
When placed in water it will dissolve.
Called electrolytes
Covalent Bonding
Non Metal Bonding
Covalent Bonds form when atoms share one or more electrons
The bond is more like a marriage rather than one atom taking over
the others electrons.Called Covalent because each
atom contributes equally!
RememberAtoms like complete outer shells.
Simplest Example is Hydrogen
• When one hydrogen encounters another hydrogen, their electrons pair up.
Hydrogen Molecule H2
• Each hydrogen atom thinks it has a full outer shell.
• Stable• Normal temperature,
hydrogen is found this way.
This type of molecule is called a Diatomic molecule
• Hydrogen
• Oxygen
• Nitrogen
• Fluorine
• Chlorine
• Bromine
More Complex
And these where mild!
Plastics
Proteins
DNA
Properties of Covalent Compounds
• Molecules are bonded weakly together(but not the single molecule)
• Low melting and boiling points
• Poor Conductors– Water needs a salt dissolved in it to conduct
electricity
• Sometimes Flammable– Organic compounds like wood
Metallic Bonds
Bonds that are formed by the attraction between positively charged metal ions and the
electrons around them
Metallic Atoms Come Close Together
Their Electrons Create a “Sea” of Electrons blending their outer shells
Basically the Valence electrons “Swim” around the Metal Ions
Keeping them together.
Properties
• Conduct electrical Current
• Malleable• Ductility• Flexible (non-brittle)
Naming Covalent Compounds
Rules
• 1. The first word is the first element.
• 2. Second word is the Second atom.– Add “ide” to the end like in Ionic compounds.
Rules
• 3. Add prefixes if more than one atom or molecule is present.– 1 mono– 2 di-– 3 tri-– 4 tetra-– 5 penta-– 6 hexa-– 7 hepta-– 8 octa-
Rules
• 4. Special cases:– Water H20
– Ammonia NH3
– Methane CH4
– There are others
You Try
• PCl3
• CO2
• SF6
• NCl3
• Phosphorus Trichloride
• Carbon Dioxide
• Sulfur Hexafloride
• Nitrogen Trichloride
Formulas from Names
Reverse the Process
Try
• Hydrogen Bromide
• Silicon Dioxide
• Oxygen Dichloride
• HBr
• SiO2
• OCl2
Homework
Photos taken from
• The Cartoon Guide To Chemistry
• Google Search “Crystals”