Module 2: Chapter 5 (Electrons and Bonding)

1 = 2 2 = 8 3 = 18 4 = 32

1 = 1s -> 2e- 2 = 2s -> 2e- 2p -> 6e- 3 = 3s -> 2e- 3p -> 6e- 3d -> 10e- 4 = 4s -> 2e- 4p -> 6e- 4d -> 10e- 4f -> 14 e-

principal quantum number, n

In order of increasing energy… 1s2s2p3s3p4s3d4p

Giving the previous noble gas in the periodic table, plus the remaining outer shell electrons

‘last in-first out’ exception of 4s, so 4s empties before 3d, as it has a slightly lower energy level

• Hydrogen and Groups 1+2 are s-block • Transition metals are d-block • Groups 3-8(0) are p-block • Extra are f-block

An orbital describes the region of space where there is a high probability of finding an electron

each orbital can only hold 2 electrons

Electrons in the same orbital have to have opposite spins - as far as possible electrons in the same sub-shell prefer to be in separate orbitals to minimize repulsion

• electron cloud is within the shape of a sphere - the greater the shell number n, the greater the number of its s-orbital

• electron cloud is within the shape of a dumb-bell • the three separate p-orbitals are at right angles to each other • the greater the shell number n, the further the p-orbital from the nucleus

the electrostatic attraction between positively and negatively charged ions

used to distinguish where the electrons originally came from

• in the compound every ion attracts oppositely charged ions in all directions • the result is a giant ionic lattice

• in general the physical properties of a substance are always explained by consideration of structure and bonding • generally most compounds have a high mp/bp (solid at room temp) • due to the very strong electrostatic attraction between oppositely charged ions, lots of energy is needed to break the lattice

• solid ionic compound will no conduct electricity as the ions can’t move and carry charge, in fixed positions in the lattice • only carry charge unless molten or dissolved

• often not always soluble in water, tend to be insoluble in most other solvents • water is polar • in a solution an ion can attract many water molecules • the compound will tend to be soluble if the attractions formed compensate for those broken down when the lattice breaks down • it is a fine balance, making predictions about solubility difficult

covalent bonding is electrostatic attraction between shared pair of electrons and the nuclei of the two bonded atoms

• a covalent bond is formed by the overlap of atomic orbitals • in a covalent bond the attraction is localised, this is in contrast to ions which can attract in all directions

4, 1, 3, 2

• an s subshell has 1 orbital • p has 3 orbitals • d has 5 orbitals • f has 7 orbitals

A dative covalent bond is a shared pair of electrons where both electrons are from the same atom.