Chapter 5 - Electrons and Bonding

How many electrons can an orbital hold

2 electrons

What are the four different sub shells

S sub shell

P sub shell

D sub shell

F sub shell

How many s-orbitals are there

1 s-orbital

How many p-orbitals are there

3 p-orbitals

How many d-orbitals are there

5 d-orbitals

How many f-orbitals are there

7 f-orbitals

What are the rules for adding electrons in electronic configuration

1. Fill orbitals in order of increasing energy

2. When there’s more than one orbital at the same energy level, these orbitals are first occupied by a single electron, only pairing when necessary

3. Each orbital can hold a maximum of 2 electrons

Define ionic bonding

The electrostatic attraction between positive and negative ions. Holds cations (positive/metal ions) and anions (negative/non-metal ions) together.

Describe structure of ionic compounds

-Each ion attracts oppositely charged ions in all directions

-This results in a giant ionic lattice

-This lattice contains billions of ions

-The actual number is only determined by the size of crystal

-All ionic compounds form a giant lattice

Ionic compounds - melting and boiling points

-Almost all ionic compounds are solid at room temperature

-This is because high temperatures are needed to provide enough energy to overcome strong electrostatic attraction between ions, hence most ionic compounds have high melting and boiling points.

-Melting points can be higher in latices containing ions with greater tonic charges, due to stronger attraction, or depending on the size of the ions.

Ionic compounds - solubility

-Many ionic compounds dissolve in polar solvents such as water. Polar water molecules break down the lattice and surround each ion.

-In a compound made of ions with large charges, the ionic attraction may be too strong so water cannot break it down so it won't be very soluble.

-Solubility requires two main processes 1) break down ionic lattice, 2) water molecules attract and surround ions

-Solubility depends on relative strengths of attractions with ionic lattice and

attractions between ions and water molecules.

Ionic compounds - electrical conductivity

-As a solid, ionic compounds do not conduct electricity, but they can once molten or dissolved in water

-In Solid state: - ions are in fixed position in giant ionic lattice

- no mobile charge carriers

so ionic compound is a non-conductor of electricity as solid.

-In liquid or dissolved in water state: - ionic lattice breaks down

- ions free to move as charge carriers

so an ionic compound is a conductor of electricity in liquid and aqueous states.

Define covalent bond

Strong electrostatic attraction between two nuclei and the shared pair of electrons between them.

What are double/triple covalent bonds

The are covalent bonds with stronger electrostatic forces between their nuclei. Since there is a stronger attraction the bond will also be shorter as the nuclei are closer together.

Define a dative covalent bond

A shared pair of electrons which have both been provided by the same atom, also known as co-ordinate bonds.

Define a lone pair

When covalent bonding happens, all electrons are paired. Some of these electrons are shared pairs called bonding pairs. Pairs which are not involved in this bonding are called lone pairs.

Why could molecules end up with more than 8 electrons in their outer shell

This is because as you go down the periodic table more electrons can take part in bonding so the molecules might expand their octet (expansion of the octet rule).

Why is attraction in an ionic bond different to attraction in a covalent bond

-An ionic bond will attract in all directions in three dimensions

-A covalent bond is localised so will only attract between the shared pair of electrons in the covalent bond

Which elements are able to expand their octet

-Only elements in period 3 or below are able to use expansion of the octet

-Expansion of the octet utilises its 3d sub shell so elements in periods 1 and 2 cannot expand