S2.1 - ionic model Flashcards
What are anions and cations?
Anions - negative ions that have gained electrons
Cations - positive ions that have lost electrons
What is an ion?
Ion - charged atoms that have gained or lost electrons.
Why do metal atoms experience a smaller ENC?
Metals experience a smaller ENC due to increased atomic size due to the large number of shells and shielding so there is a weaker attraction.
Why do metal ions form positive ions?
Metal atoms form positive ions as they have low ionization energies.
How is sodium chloride formed?
One electron is transferred from sodium to chloride.
How does attraction between water ions increase?
Attraction increases with ionic charge but removing multiple electrons has an energy cost.
What ions can Na form?
Na+ and Na3+ readily but not Na2+ and Na4+
Why are anions more attractive with increased charge?
Anions are more attractive with increased charge as they readily accept an electron ti their outer energy level.
Why is addition of electrons harder with increased charge?
There is increasing negative charge of the ion due to increased electron-electron repulsion.
Why are nobles gases unreactive?
Noble gases are unreactive due to their high ionization energies and complete energy levels, so adding an electron would need to add an extra shell which would be lost.
What are properties of transition metals?
Transition metals have a wide range of oxidation states that is related to successive ionization energy patterns.
What happens when ions have a charge greater than +3?
Ions with a charge greater than +3 show a covalent character as they have a large charge density as they polarize negative ions and increase the covalent character of the compound.
Why is the formation of Ca3+ unfavourable?
3rd ionization energy prohibits further electron loss.
How can you determine maximum oxidation states?
The maximum oxidation state is reached when the linear pattern ends.
What is a polyatomic ion?
Ions made up of more than 1 atom that have lost or gained electrons.
What type of bonding is present in polyatomic ions?
Ionic bonding
What is an ionic bond?
Ionic bond - attraction between positive metal ion and negative electron.
What is the structure for ionic compounds?
Giant ionic lattic
What is the structure of NaCl?
Cl- = has a smaller radius due to larger ENC
Na+ = has a larger radius due to smaller ENC
What is a co-ordination number?
Number of atoms that surround individual atoms in a lattice.
What is lattice enthalpy?
Lattice enthalpy - energy needed to break or make the ionic bond in a lattice.
- Measure of the strength of a bond.
How can you increase lattice enthalpy?
- Increase in ionic charge
- Decrease in ionic radii
- Change in charge density
Why do ionic compounds have high melting and boiling points?
Ionic compounds have high melting and boiling points as they have a strong electrostatic attraction between electrons and positive ions.
How does charge affect melting and boiling points?
Larger charge = Higher melting and boiling point as there is a higher electrostatic attraction and therefore a stronger bond.
Why are ionic compounds non-volatile?
Ionic compounds are non-volatile as they are held in a lattice, meaning that there are no free molecules to move away and break from the structure, which would require high amounts of energy.
When are ionic compounds soluble?
Ionic compounds are soluble in polar solvents such as water since like substances dissolve.
How can you tell if a substance has dissolved or not?
Dissolved - if the electrostatic attraction between ions is weaker than water’s attraction to them.
Not dissolved - if the electrostatic attraction between ions is stronger than water’s attraction to them.
What does hydrated mean?
Hydrated - when ions are surrounded by water molecules.
What does solvated mean?
Solvated - when ions are surrounded by other solvent molecules.
Why do ionic compounds conduct electricity?
Ionic compounds can conduct electricity as they have delocalised electrons which can move around the structure and carry charge.
Why are ionic compounds brittle?
Ionic compounds are brittle as crystals break when a force is applied since the pressure forces like charges together so that they repel each other to the point of breaking.
When is something ionic, covalent or polar covalent?
Ionic - difference in electronegativity > 1.8
Covalent - difference in electronegativity < 0.4
Polar covalent - difference in electronegativity is between 0.4 and 1.8.
Why are period 3 oxides less ionic across?
It is shown by a decrease in melting points and a decrease in the ability to conduct electricity in the molten state.
How do you work out % ionic character?
% ionic character = (difference in electronegativity / 3.2) x 100
How do you calculate lattice enthalpy for 1 mole of ion pairs?
Lattice enthalpy for 1 mole = (Knm / Rm+ + Rx-)
K - constant for a structure that takes into account one of the many ion interactions and depends on the geometry of the lattice.
n and m - magnitude of the charge of the ions
Rm+ and Rx- - ionic radii
What is the relationship between energy needed to separate 2 ions and ionic charge?
An increase in ionic charge increases the ionic attraction between ions and increases lattice enthalpy.
What is the relationship between energy needed to separate 2 ions and ionic radius?
An increase in ionic radius of one of the ions decreases the attraction between the ions and decreases the lattice enthalpy.
What is the relationship between energy needed to separate 2 ions and charge density?
The lattice enthalpy is greater for ions with a larger charge density as they have a small radius and are highly charged.
