Summary (Chemical Bonding)

Atomic Structure

Atoms are made of:

- electron (-)

- proton (+)

- neutron

 

Proton and neutron are found in the nucleon which is in the nucleus.

Atomic number/Proton number = the number of proton

Mass number = the number of proton + the number of neutron

Isotopes are atoms of the same elements with the same number of protons but different number of neutrons.

Isotopes have the same chemical properties but slightly different physical properties, they differ because the relative masses of the isotopes differ.

 

Periodic table is arranged in order of increasing proton numbers.

The outer shell of an atom is the valence shell.

Valence electrons determine what group an element is in.

Chemical Bonding

Ionic bonding

 

Noble gases are stable and unreactive.

Atoms gain a full shell through losing, gaining or sharing valence electrons.

Metals form cations whereas Non-metals form anions.

Atoms of metals become positive ions when they lose valence electrons.

Atoms of non-metals become negative ions when they gain electron.

Metal reacts with non-metal through Ionic Bonding to form a compound.

An example is when sodium bond with chloride.

Show it throught the dot-and-cross diagram. Remember to put:

- What dot represents

- What cross represents

- Square brackets

- The charge of the ion

- Which is which ion

- The end electronic configuration

Ionic compounds form giant ionic structure.

They are tightly pack

The ions are tightly held together by the ionic bond produce the ions. A large amount is needed to break the bond of the ions to change it from solid to liquid state. As  result ionic compund are solid a room temperature. They have high melting and high boiling points.

Ionic compound can only be tested if it conducts electricity when it is in the aqueous state.

Ionic Compound are soluble in water but not in organic solvent such as ethonal, petrol.

Covalent Bonding

Non-metal react with each other through covalent bonding.

It happens when atoms SHARE their atoms.

When a group or two or more atoms are held firmly together, they form a molecule instead of an ion.

How to draw the dot and cross diagram:

-Remember to say this dot represents what

-Remember to say the cross represents what

-The two circles must be ‘connected’

Single covalent bond represented by –

Double covalent bond is represented by =

So on and so forth…

Simple covalent substances, especially the ones made up of small molecules have high volatility (low melting and boiling points) As the forces pulling the atoms together are weak causing very little heat energy needed to overcome the intermolecular forces.

Simple covalent substances made up of larger molecules are solids at room temperature.

Most covalent molecules are insoluble in water but soluble in organic solvent.

Most covalent electricity do not conduct electricity whether in solid, liquid or solid state. This is because they do not have free-moving ions or electrons to conduct electricity.

There are exceptions! Carbon in the form of graphite conducts electricity

Hydrogen chloride, sulphur dioxide and ammonia react with water to form solutions that conduct electricity.