Unit 1 - Structure and Bonding: Bonding Types

Question 1

Covalent Bonding
Pure Covalent Bonds

Answer 1

In a covalent bond, atoms share pairs of electrons. The covalent bond is a result of two positive nuclei being held together by their common attraction for the shared pair of electrons.

In covalent elements, both atoms have the same attraction for the shared electrons (electronegativity). When the electrons are shared equally, a pure covalent bond (non-polar covalent bond) is formed.

A pure covalent bond has no ionic character at all.

Question 2

Covalent Bonding
Polar Covalent Bonds

Answer 2

Polar covalent bonds are formed when the attraction of the atoms for the pair of bonding electrons is different.

Simply, a polar covalent bond is formed when when a shared pair of elctrons are not shared equally. This is due to one of the elements having a higher electronegativity than the other.

Question 3

Polar Covalent Bond Example

Answer 3

Hδ+ –> Fδ-

The symbols delta postive and delta negative indicate partial charges on atoms.

Fluorine has a greater electronegativity than Hydrogen. This means it will pull the bonding electrons towards itself. This makes Fluroine slightly negative and Hydrogen slightly positive. This is known as a dipole.

Question 4

Ionic Bonding

Answer 4

In ionic bonding, the element with the greater atttraction (higher electronegativity [non-metal]) gains electrons to form a negative ion. The element with the smaller attraction (lower electronegativity) loses electrons to form a positive ion.

Ionic bonds are the electrostatic attraction between positive and negative ions.

Ionic compounds form lattice structures of oppositely charged ions.

Question 5

Bonding Continuum

Answer 5

Pure covalent bonding and ionic bonding can be considered as being opposite ends of a bonding continuum with polar covalent bonding lying between these two extremes.
The bonding continuum shows the ‘continuum’ of states from covalent to ionic bonds.

Question 6

Ionic Formulae

Answer 6

A correct ionic formula containes ions with the same total number of positive and negative charges.

E.g Na+Cl- , Mg2+O2- , Na+2O2- , Cu2+(No-3)2

Question 7

Compounds formed…

Physical Properties and Bonding

Answer 7

Compounds formed between metals and non-metals are often, but not always, ionic.