2.2 - Electrons, Bonding and Structure Flashcards
How many electrons are in the first 4 quantum energy levels (shells)?
1st = 2 2nd = 8 3rd = 18 4th = 32
What is an orbital?
A region of space around the nucleus of an atom that can hold up to two electrons with opposite spins.
Describe the shape of s and p-orbitals.
S = circle P = figure of eight
How many orbitals and electrons are in the sub-shells s, p, and d?
S = 1 orbital, 2 electrons P = 3 orbitals, 6 electrons D = 5 orbitals, 10 electrons
Describe the relative energies of orbitals in sub-shells up to 4p.
From least to most: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p
Note - this is a general trend and can be broken.
What are the general rules to remember for electron configurations?
4s fills up before 3d
4s leaves before 3d
Define ionic bonding.
The electrostatic attraction between positive and negative ions.
What are the ionic charges of groups 1, 2, 3, 4, 5, 6 and 7?
1 = 1+ 2 = 2+ 3 = 3+ 4 = 5 = 3- 6 = 2- 7 = 1-
What is a compound ion?
A group of covalently bonded atoms that have a charge.
Give the formulae of the following compound ions: nitrate, carbonate, sulphate and ammonium.
What about these: hydroxide, silver and zinc.
Nitrate = NO3 - Carbonate = CO3 2- Sulphate = SO4 2- Ammonium = NH4 + Hydroxide = OH - Silver = Ag + Zinc = Zn 2+
Describe the difference between a giant and a simple structure.
Giant - a substance with a huge network of intramolecular forces.
Simple - a substance with a few covalent bonds in it forming a small molecule (e.g. CO2). Held together by intermolecular forces.
Describe the structure of ionic crystals.
Ionic crystals are made up of a giant ionic lattice. A lattice is a regular structure. A giant ionic lattice is made up of a giant network of ions that are electrostatically attracted to each other.
Describe the bonding and structure of ionic compounds, as well as melting/boiling points and hardness.
Giant structure with ionic bonding (giant ionic lattice).
Very high melting and boiling points - a large amount of energy needs to be put in to overcome the strong electrostatic attractions and separate the ions.
Hard to scratch due to the strong nature of the bonding which requires such a large amount of energy to make any changes to the structure. Very brittle as the ions will only accept being in one particular arrangement (due to their opposite charges).
Describe the electrical conductivity and solubility of ionic compounds.
Electrical conductivity in solids - none. The ions are held in a fixed position by the strong ionic bonds. This means they are not free to move. When molten or in solution - conducts. The ions are now free to move as they are no longer held together in the lattice structure.
Many are soluble in water due to the attraction between the ions and the polar water molecules. Insoluble in non-polar solvents.
Define covalent bonding.
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
What is a lone pair?
Non-bonded electron pairs.
What is a dative bond?
The electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms where both electrons come from the same atom.
What is meant by the term average bond enthalpy?
A measure of the energy required to break a covalent bond. The higher the average bond enthalpy, the stronger the covalent bond (stronger bonds will require more energy to break).
How is the shape of a molecule determined?
Electrons are negatively charged. Electron pairs repel one another equally. Lone pairs repel more than bonded pairs. It is determined by the number of bonded pairs.
What is the shape and bond angle of methane? How many pairs does it have?
Tetrahedral - 109.5°
4 bonded pairs, 0 lone pairs.
What is the shape and bond angle of ammonia? How many pairs does it have?
Triangular pyramidal - 107°
3 bonded pairs, 1 lone pair.
What is the shape and bond angle of water? How many pairs does it have?
Non-linear (bent) - 104.5°
2 bonded pairs, 2 lone pairs.
What is the shape and bond angle of carbon dioxide? How many pairs does it have?
Linear - 180°
2 double bonded pairs, 0 lone pairs.
What is the shape and bond angle of boron triflouride? How many pairs does it have?
Trigonal planar - 120°
3 bonded pairs, 0 lone pairs.