M2 Electrons and Bonding Flashcards
Define a shell
A shell is an energy level. The further from the nucleus, the higher the energy level.
Define an atomic orbital
An atomic orbital is a region around the nucleus that can hold up to 2 electrons, with opposite spins.
What are the sub-shells?
A shell can contain different sub shells: s, p, d and f.
Describe the s sub-shell
Number of orbitals: 1
Maximum electrons: 2
Orbital structure: sphere
Describe the p sub-shell
Number of orbitals: 3
Maximum electrons: 6
Structure: 3d dumbbell shape
Describe the d sub-shell
Number of orbitals: 5
Maximum electrons: 10
Describe the f sub-shell
Number of orbitals: 7
Maximum electrons: 14
Electron configuration of argon (18)
1s^2 2s^2 2p^6 3s^2 3p^6
Rule with 3d and 4s
The highest energy level of the third shell overlaps with the lowest energy level of the fourth shell, therefore 4s is filled before 3d. But is written 3d before 4s
eg. Sc: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1
Describe the rules for filling orbitals
- Electrons fill into sub-shells with the lowest energy first
- Orbitals within a sub-shell will fill singly before pairing up
- Paired electrons have opposite spin
Define ionic bonding
Electrostatic attraction between positive and negative ions
Describe the structure of ionic compounds
- Each ion attracts oppositely charged ions in all directions, resulting in a giant ionic lattice containing millions of ions.
Describe the melting and boiling points of ionic compounds
- Nearly all solid at room temperature as there is not enough energy to overcome the strong forces of electrostatic attraction between oppositely charged ions.
- High temperatures are needed to provide a large amount of energy to overcome the strong electrostatic attraction between ions, therefore ionic compounds have high melting and boiling points.
- Melting and boiling points are higher for lattices containing ions with greater ionic charges, as there is a stronger force of attraction between ions. Size of ions also affects the force of electrostatic attraction.
Describe the solubility of ionic compounds
- Many ionic compounds dissolve in polar solvents (such as water). Polar molecules break down the lattice and surround each ion in solution.
- In a compound made of ions with large charges, the ionic attraction may be too strong for water to break it down the lattice, so the compound is not soluble.
- The positive ions are attracted to the negative end of the water molecule, and the negative ions are attracted to the positive end of the water molecule.
Are common salts of sodium, potassium and ammonium soluble?
Yes
Are nitrates soluble?
Yes
Are common carbonates and hydroxides soluble?
No, except sodium, potassium and ammonium ones
Are common chlorides soluble?
Yes, except silver and lead chloride
Are common sulfates soluble?
Yes, except lead, barium and calcium sulfate
What does solubility depend on?
- Solubility requires the ionic lattice to be broken down and water molecules must attract and surround the ions.
- The solubility of an ionic compound in water therefore depends on the relative strengths of attractions within the giant ionic lattice, and the attractions between ions and water molecules.
- Attractions in the giant lattice have the greater effect, and solubility decreases as ionic charge increases.
Describe the electrical conductivity of ionic compounds
- When solid, an ionic compound does not conduct electricity, but once melted or dissolved it does conduct electricity.
- In solid: the ions are fixed in the giant ionic lattice so there are no mobile charge carriers.
- In liquid: the solid ionic lattice breaks down and the ions are free to move as mobile charge carriers.
Define a covalent bond
A covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What does covalent bonding occur in?
Non-metallic elements eg. H2
Compounds of non-metallic elements, eg. H2O
Polyatomic ions, eg. NH4 +
What is single covalent bonding?
Two atoms share a pair of electrons
What is multiple covalent bonding?
In a double bond, the electrostatic attraction is shared between two pairs of electrons and the nuclei of the bonding atoms
What is dative covalent bonding?
A dative covalent bond is a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only.
The shared electron pair was originally a lone pair of electrons on one of the bonded atoms.
What is a triple covalent bond?
The electrostatic attraction is between three shared pairs of electrons and the nuclei of the bonding atoms.
What is average bond enthalpy?
Average bond enthalpy serves as a measurement of covalent bond strength. The larger the value of average bond enthalpy, but the stronger the covalent bond.
