Ionic bonding Flashcards
Ionic bonding
Strong electrostatic attraction between oppositely charged ions
What is an ionic structure?
A Solid material consisting of a regular array of oppositely charged ions through a lattice structure
How are ions arranged in a lattice?
In a way where the oppositely charged ions attraction is greater than the repulsion between similarly charged ions
Do bond angles and the ions orientation matter in an ionic structure?
No because the electrostatic attraction is not directional therefore doesn’t effect the shape unlike covalent bonding
Do the ionic bonds actually hold the shape together?
No but the total interactions ions have with each other which is the lattice energy is what does
What are the charges like in an ionic compound?
They balance each other out exactly so overall charge is 0
What affect the strength of an ionic bond?
The stronger the electrostatic attraction between oppositely charged ions which is affected by:
Ionic charges
Ionic radii
Ionic charges affect on ionic bond strength
The greater the charge on an ion, the stronger the ionic bond
Therefore stronger melting/boiling points
Ionic radii affect on ionic bond strength
Because electrostatic attraction gets weaker by distance:
Smaller ions with smaller radii are packed closer together thus have stronger ionic bonding
Therefore stronger melting/boiling points
What does the size of an ion depend upon?
It’s number of electron shells and it’s atomic number
Trend of ionic radii
-Increases going down a group
-Across a collection of isoelectronic ions, the radius decreases as atomic number increases
Ionic radii down a group
Increases because going down the group the atomic number increases
Therefore increased number of electrons occupy extra electron shells
What are isoelectronic radii?
Ions of different atoms but with the same number of electrons
because they lose or gain electrons to have a full outer shell
Isoelectronic radii trend?
The number of electrons stay the same however proton number increases
So electrons are attracted to the nucleus more as you go across, decreasing radii because they are pulled in
What structures does ionic bonding form
Giant ionic lattices
Why do ionic structure form?
Because each ion is electrostatically attracted attracted in all directions to the ions of opposite charges eg can form a lattice because the ionic bonds forms between all ions
Properties of ionic compounds
High melting point
Soluble in polar solvents, insoluble in non polar solvents
No conduction of electricity when solid but conduction when molten/ dissolved
Brittle
Why do ionic compounds have high melting points?
Because the ions are held together by strong electrostatic attraction between oppositely charged ions which requires a lot of energy to overcome
Why do ionic compounds dissolve in polar solvents?
Because the particles are charged thus are ions
Therefore the ions are pulled apart by polar molecules from a polar solvent
Why do ionic compounds conduct electricity only when molten or dissolved?
Because as a solid, the ions are in a fixed position by strong ionic bonds and can’t carry a charge but when dissolved/ molten the charged particles (ions) are free to carry it
Why are ionic compounds brittle?
If a force was applied to pull layers of ionic compound over each other, the similarly charged ions would repel each other. This repulsion is strong, causing ionic compounds to break when hammered (thus brittle)
Migration of ions: copper ii chromate vi
When you electrolyse (electrolysis) copper ii chromate vi on wet filter paper the ions will move to the opposite charged electrode
Which electrode does copper ii migrate to?
The cathode (negative electrode) because it’s a positive metal ion
What colour is at the cathode?
Blue because the copper ii ions migrate there thus causes a blue colour
What colour is copper ii ions?
Blue
What electrode does chromate vi migrate to?
Anode because they are negative charged ions
What colour is the anode?
Yellow because the chromate ions are discharged there which are yellow
What colour are chromate ions?
Yellow
What colour is copper ii chromate vi?
Green because it is a mixture of:
Copper ii ions = blue
Chromate vi ions = yellow
