Chapter 5 - Electrons and Bonding Flashcards
Electron structure, Ionic bonding and structure and Covalent bonding.
Shells are regarded as what?
Energy levels
What happens to energy as the shell number increases?
Energy increases
What is the shell number referred to as?
Principal quantum number
What are shells made up of?
Atomic orbitals
How many electrons can be held in an orbital?
One or two, no more.
What can an electron be thought of as?
A negative-charge cloud with the shape of the orbital, called an electron cloud.
What are the different sub shells?how many orbitals and electrons do they have?
S-subshell- 1 orbital - 2 electrons
P-subshell- 3 orbitals- 6 electrons
D-subshell- 5 orbitals- 10 electrons
F-orbitals- 7 orbitals- 14 electrons
How many orbitals does each type contain?
S - one
P - three
D - five
F - seven
How many electrons can be held in each orbital type?
S - two
P - six
D - ten
F - fourteen
What is the shape of an s-orbital?
Spherical
What is the shape of a p-orbital?
Dumbbell
What are the rules of orbital fillings?
Orbitals fill in order of increasing energy.
Electrons pair with opposite spins.
Orbitals with the same energy are occupied singly first.
Explain the rule of orbitals filling in order of increasing energy
1s is filled first.
For n=2 shell, filling order is: 2s, 2p
For n=3 shell, filling order is 3s, 3p, 3d
Where does the electrons filling subshells in energy level order rule cause confusion?
The 3d sub-shell has higher energy than the 4s.
So the 4s fills before the 3d.
Explain the rule of electrons pair with opposite spins
Electrons are negatively charged and repel one another.
Electrons can have spin up or spin down.
If electrons have opposite spin, the charge repulsion is counteracted enough for both to be in the orbital.
Explain the rule of orbitals with the same energy are occupied singly first
Within a sub shell, the orbitals have the same energy. One electron occupies each orbital before pairing begins. This prevents repulsion until no unoccupied orbitals remain.
How can electron configuration be shortened?
1s2 can be expressed as [He].
1s2 2s2 2p6 can be expressed as [Ne].
1s2 2s2 2p6 3s2 3p6 can be expressed as [Ar].
What happens in terms of energy sub-shells when forming ions?
The highest energy sub-shells lose or gain electrons.
What is ionic bonding?
The electrostatic attraction between positive and negative ions.
metal and non metal
What is the result of ions attracting oppositely charged ions in all directions?
Giant ionic lattice
How are the melting and boiling points of ionic compounds explained?
High temperatures are required to provide the energy sufficient to overcome the strong electrostatic attraction between the ions.
What happens to the melting points for giant ionic lattices, when ionic charge increases?
Melting point increases as there is a stronger attraction between ions.
Are ionic compounds soluble?
They dissolve in polar solvents such as water.
What does solubility require for an ionic lattice?
The ionic lattice must be broken down.
Water molecules must attract and surround the ions.
What does solubility (of ionic compounds) depend on?
The relative strengths of the attractions within the giant ionic lattice and the attractions between ions and water molecules.
When can ionic compounds conduct electricity?
Not in the solid state.
When molten or dissolved in water.
Why can’t ionic compounds conduct electricity when solid?
The ions are in a fixed position.
There are no mobile charge carriers.
Why can ionic compounds conduct electricity when molten or dissolved in water?
The solid ionic lattice breaks down.
The ions are now free to move as mobile charge carriers.
Summarise the properties of most ionic compounds
High melting and boiling points.
Tend to dissolve in polar solvents such as water.
Conduct electricity only in the liquid state or in aqueous solution.
What is covalent bonding?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
between non metals
What actually is a covalent bond?
The overlap of atomic orbitals, each containing one electron, to give a shared pair of electrons.
How does covalent bonding differ to ionic bonding?
The attraction is localised, acting only on the shared pair of electrons and the two nuclei of the bonded atoms.
How can covalent bonding be displayed?
With dot and cross diagrams.
What is a multiple covalent bond?
Two atoms share more than one pair of electrons.
What is a double bond?
The electrostatic attraction is between two shared pairs of electrons, and the nuclei of the bonding atoms.
What is a triple bond?
The electrostatic attraction is between three shared pairs of electrons, and the nuclei of the bonding atoms.
What is a dative covalent bond?
The shared pair of electrons has been supplied by one of the bonding atoms only. Originally a lone pair.
Give an example of a dative covalent bond
An ammonia molecule donates its lone pair of electrons to an H+ ion.
Forming an ammonium ion.
NH3 goes to NH4+
What is average bond enthalpy?
A measurement of covalent bond strength.
Larger value = stronger bond
