Chapter 5 Electrons and bonding Flashcards
Shells
Energy levels
Quantic number, n
The energy level number
What are shells made up of
Atomic orbitals
Atomic orbitals
A region around the nucleus that can hold up to 2 electrons, with opposite spins
Types of atomic orbitals
- s-
- p-
- d-
- f-
s-orbital
electron cloud is in the shape of a sphere
p-orbital
- electron cloud is in the shape of a dumbbell
- there are 3 p-orbitals, at right angles to eachother
d-orbitals
Sub-shells
Orbitals of the same type are grouped together as these
Ionic bonding
Electrostatic attraction between oppositely charged ions
Structure of ionic compounds
Giant ionic lattice
Regular arrangement of alternate pattern of positive and negative ions
Properties of ionic compounds
- High melting and boiling points -> lots of energy needed to overcome strong electrostatic attraction between the ions
- as the charge increases, m.p. and b.p. increase
- Soluble in polar solvents - breaks down the lattice and water molecules attract + surround each ion
- Electrical conductivity - do not conduct in solid state because the ions are not mobile
Covalent bonding
Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
When does covalent bonding occur
- Non-metallic elements
- Compounds of non-metallic elements
- Polyatomic ions
What is a covalent bond made up of
Overlap of atomic orbitals, each containing 1 electron -> gives a shared pair of electrons
The shared pair of electrons is attracted to the nuclei of both the bonding atoms
How does ionic bonding act
In all directions
How does covalent bonding act
Localised - acts only between the shared pair of electrons and the nuclei of the bonding atoms
Unusual covalent bonding
Boron -> only has 3 outer shell electrons so can only produce 3 covalent bonds = 6 electrons in outer shell
Expansion of the octet
When sulfur pairs all 6 of its outer shell electrons = 12 outer shell electrons
Multiple covalent bond
Exit when 2 atoms share more than 1 pair of electrons
Dative covalent bond/coordinate bond
A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only
Examples of dative covalent bonds
NH4+
How is a dative covalent bond shown?
Arrow from the bonding atoms whose electrons they are
Average bond enthalpy
A measurement of covalent bond strength
The larger the average bond enthalpy, the stronger the covalent bond
