Topic 4.2: Covalent bonding Flashcards
What is the tendency of most elements at chemical reactions regarding electron configuration?
Gain electrons to achieve the stable e- configuration of a noble gas by sharing an electron pair
Definition of a covalent bond
The electrostatic attraction between a shared pair of electrons and the positively charged nuclei.
When are atoms more likely to form a covalent bond?q
When they have similar electronegativities
a) Both atoms have the same affinity for electrons and neither tends to donate them.
b) They share electrons to achieve a noble gas e- configuration,
Electrons in a double and triple bond
4 electrons (2 e- pairs) 6 electrons (3 e- pairs)
Definition of bond length
Measure of the distance between two bonded nuclei
Explanation of the tendency of bond length as # covalent bonds increases
a) Bond length decreases as the number of electron pair increases
b) This is because there will be a greater attractive force between the two nuclei
Definition of bond strength
Measure of the energy required to break the bond
Explanation of the tendency of bond strength as # covalent bonds increases
Bond strength increases as the number of electron pairs increases.
a) As the number of electrons in a bond increases, the nuclei and the bonded electrons have a stronger electrostatic force of attraction
b) The more energy is required to break them
Explanation of the tendency of bond strength as bond length increases in elements with single bonds
Single bond between elements gets weaker as the bond gets longer
a) As the atoms get bigger, the electron pair in the covalent bond is further away from the nuclei of the atoms making up the bond
b) If the electron pair is further away from the nuclei, it is less strongly attracted, and the bond is weaker
Do different atoms share and attract electron pair in a covalent bond equally? Why?
No. How strongly the electrons are attracted depends on the size of the individual atoms and their nuclear charge (electronegativity)
Definition of bond polarity
Measure of how equally electrons in a covalent bond are shared
What happens when electronegativities between two atoms are not equal?
a) Electrons are not shared equally
b) A partial ionic charge develops (polar / dipole)
What affects the extent of polarity in a covalent bond?
It depends on how big a difference exists in the electronegativity values of the two bonded atoms.
Types of covalent bond according to polarity
a) Polar. Unsymmetrical disribution of electron density (S+ => S-)
b) Non-polar. Equal sharing of bond electrons
Transfer of electrons in the following bonds:
a) Ionic
b) Polar covalent
c) Non polar covalent
a) Complete transfer
b) Unequal sharing of e-
c) Equal sharing of e-
