Lecture 7-Ionic Bonding Flashcards
What is a chemical bond?
The attractive force that holds 2/+ atoms together in a molecule
Why do atoms combine?
To gain stability
How do e- in atoms distribute themselves?
In the most stable/lowest energy configuration
How can a combined molecule achieve lower energy?
By rearranging e- between atoms
All element except who show a strong tendency to join with other elements to form compounds/
Noble gases
What group of elements obey the 18 e- rule and not the octet rule?
Transition metals
The strength of an electrostatic interaction is what?
- Proportional to the size of the charge
- Inversely proportional to distance^2
What operates between 2 atoms when they come close together?
Attractive + repulsive forces
When do like charges repel?
E-/E- + nucleus/nucleus
When do opposite charges attract?
E-/nucleus
What is electronegativity?
The ability of an atom to attract toward itself the e- in a chemical bond
What does electronegativity depend on?
- N.O of protons
- Distance from the nucleus
- Amount of screening by inner e-
What is the most electronegative element and why?
Fluorine
- Small
- High nuclear charge
What does covalent bonding show?
Polarity of bonds
What does ionic bonding show?
Initial transfer of e- + direction
How are ionic bonds formed?
When 1/+ e- are FULLY transferred between atoms
Where does ionic bonding take place?
Between metals + non-metals
Metal atoms do what to attain noble gas structure?
Lose e- —–> cations (positive ions)
Non-metal atoms will do what to attain noble gas structure?
Gain e- —–> anions (negative ions)
What does the formation of an ionic bond involve?
A DECREASE in energy compared to 2 isolated atoms
The valency of an ion = what?
Its charge
Is an ionic bond non-directional?
YES
What does non-directionality mean?
The strength of the bond depends upon DISTANCE not directions
What do ionic compounds dissolve + disassociate in?
Polar solvents
Are ionic compounds charged overall?
NO
When do ionic compounds conduct electricity?
When molten / in solution
What do ionic compounds form?
Regular crystalline solids with high melting temperatures
In an ionic lattice, what is every ion attracted to?
All other ions with the opposite charge
What is lattice energy?
The enthalpy of formation energy change forming 1 mole of ionic solid from its gaseous ions - measures bond strength
What factors favour an easy cation formation?
Low ionization energy of the METAL
What factors favour an easy anion formation?
- High e- affinity/electronegativity of the non-metal
- Small size of NON-METAL
- Low charge on ANION
- Large electronegativity DIFFERENCE between combining atoms
- High lattice energy of IONIC COMPOUND
What ions are smaller than parent ions?
Positive ions
What is polarisation?
Distortion of the e- cloud of an atom
How does a small ion have more polarizing power?
Higher charge density
How does a large ion have great polarizability?
Larger its N.O of e-
DO anions / cations have more polarising power and why?
CATIONS , because they are generally smaller
If a negative ion is distorted ,because of polarisation it has what?
COVALENT character
What is an ideal ionic compound composed of?
Completely separate spherical ions
When is an ionic compound likely to have covalent character?
The cation = small +/ high charge (highly polarising)
The anion = large +/ high charge (highly polarisable)
What are polyatomic ions?
Ions made up of more than 1 type of atom
What type of binding is present in polyatomic ions?
Covalent
Ammonium
NH4+
NITRATE
NO3-
CYANIDE
CN-
SULFATE
SO4 2-
HYDROXIDE
HO-
CARBONATE
C03 2-
PEROXIDE
02 2-
PHOSPHATE
P04 3-
ACETATE
CH3CO2-
PERMANGENATE
Mn04-
OXALATE
C2O4 2-
DICHROMATE
CrO7 2-
What is the first word of an ionic compound name?
The CATION (except ammonium)
What is the second word of an ionic compound name?
The ANION
If the second name of an ionic compound is polyatomic, what does it end in?
The name of the polyatomic ion
If the second name of an ionic compound is the element what does it end in?
-ide
