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Transcript of Chemical Bonding
Formation of Ions
What is an Ion?
Anything that has an electric charge. positive (+) or negative (-)
ex: Al (3+) or O (2-)
We have names for a positive ion and a negative ion.
What type of Ion does an element form?
would it be positive, negative or does it make an ion at all?
All atoms want to get their outer energy level completely full of electrons. Why?
Remember how we get that + or - charge?
protons (+) and electrons (-) are different.
Ex: Mg (2+)
ion with a positive charge (+)
how does an atom get a positive charge?
Just remember "Pawsicat"
Electrons are lost!!!
Also the "t" in cation looks like a positive sign.
we have more protons than electrons so positive charge
Ion with a negative charge
key to remember:
it is a "negative'' ion an anion
how does an atom get a negative charge?
We have more electrons than protons so negative charge
Electrons are gained!!!
When the outer energy level is full, the atom is STABLE.
It is sitting on the couch watching pretty little liars with a full stomach and content
in our class we will make the assumption that the outer energy level needs 8 electrons in order to be stable
EVERY atom wants to get 8 valence electrons in order to be happy and stable.
Which elements are already happy?
the Noble Gases!!
This is why the nobel gases don't react with other elements. they are already stable and happy.
How does an atom become stable and get 8 valence electrons?
It can become an ION and get to stable number 8
What is the Bohr Model Diagram for Beryllium (Be)?
how could the atom get 8 electrons in its outermost energy level?
what is the Bohr Model Diagram for Oxygen (O)?
how could the atom get 8 valence electrons in its outermost energy level?
gain or lose e-?
When two Ions of opposite charge (+ and -) attract each other
When a positive cation and negative anion are attracted to each other.
This occurs by the
This is why the chemical formula for Salt is NaCl
In an Ionic bonded compound the compound as a whole must be neutral!!!
What if we put together Calcium (Ca) and Bromine (Br)?
What if Calcium and Oxygen bond?
It wants to look like this???
Lewis dot for Ca?
Lewis dot for Br?
What is a bond?
the force that hold atoms or ions together in a compound
The bond length, bond angle and strength of the bond vary in every molecule
What does each atom do to become stable?
What is the charge on Ca?
What is the charge on Br?
What would be the formula?
Faster way to find formula
What is the formula when K bonds with P?
Charge of K?
Charge of P?
How many of each atom do we need in order for the overall charge to be neutral?
EX: Al & O bond
Characteristics of Ionic Bonds
Occurs when a positive cation and a negative anion attract.
Transfer of Electrons: cation gives/donates electrons and anions receive/take electrons.
Forms a crystal lattice structure (regular pattern
Strength between bonds is HIGH (high melting and boiling point). But is also brittle
Is soluble in water (dissolves)
Conducts electricity when dissolved in water.
Naming Ionic Compounds
The Positive ion (cation) name is unchanged
The Negative ion (anion) changes its ending to -IDE
The Negative polyatomic ion (anion) name is unchanged
The Positive Transition metal ion (cation) has a roman numeral to indicate charge
Covalent = NM + NM
So what happens when two nonmetals come together?
Cl & Cl
They both want to accept/gain electrons to be stable
How can both Cl become stable?
In covalent molecules electrons are SHARED between atoms
Covalent Lewis Dot Structures
Acids without Polyatomic
HYDRO- as prefix and -IC as the ending
EX: HCl = Hydrochloric acid
Always has an H out front in symbol (Cation)
Always has ACID at end of name
Acids with Polyatomic
Polyatomic ends in -ITE: Change ending of name to -OUS
EX: HNO2 = Nitrous acid
Polyatomic ends in -ate: Change ending of name to -IC
EX: HNO3 = Nitric acid
Do not have a regular crystalline (lattice) structure
Low strength of bonds (low melting/boiling point)
Do not dissolve in water
Do not conduct electricity when dissolved in water
draw dot structure
connect lone dots so atoms are happy
redraw so its pretty
Naming Covalent Molecules
When naming covalent molecules PREFIXES are used
Never use prefix -mono on first element
Second element still has the ending -ide
Shared pair: the pair of e- shared between Br & F
notice both Br & F donated 1 electron to be shared between them
Lone pair (unshared pair): pair of electrons not involved in bonding and belonging to one atom
single bond: one pair of electrons (2) being shared between two atoms
Valence Bond Theory
A nonpolar covalent bond can be represented graphically
What does this graph show? What are the axis telling us?
The bond length is determined by the potential energy.
Bond length: distance between bonded atoms nuclei at the minimum potential energy. (when attractive and repulsive forces are balanced)
Bond energy: Energy required to break apart that bond
Positive nuclei & inner electrons with mobile valence electrons
Strong bonds (high melting pt)
Conductor of electricity & heat
all due to delocalization of electrons: They have great cohesive force, and are mobile.
1. Interstitial: atom of one element fills space of another element
different radius. Smaller radius in place of bigger radius
results in a harder, more rigid structure
2. Substitutional: Comparable radius sustitutes in for another atom
1. Write down first element (cation)
If a transition metal use Roman numeral (I, II, III, etc.) to show charge
2. Write down second element/polyatomic (anion)
If element, change ending to -ide
If polyatomic, write as is