3.1.3.2 Nature of Covalent and Dative Covalent Bonds
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What is dative covalent bonding?
When both of the shared electrons come from the same atom
What are the properties of small covalent bonds?
Low melting/boiling points Don’t conduct electricity Are electrical insulators Small covalent molecules that are polar or can form hydrogen bonds are soluble
What are the properties of giant covalent bonds?
Extremely high melting/boiling points Electrical insulators Don’t conduct electricity Aren’t soluble in water
What are covalent bonds?
Where atoms share electrons to have a noble gas arrangement Formed between a pair of non-metal atoms
What is a molecule?
A small group of covalently bonded atoms
How does a covalent bond work?
The atoms are held together by the electrostatic attraction between the nuclei and shared electrons
How do you represent two shared electrons in a covalent bond?
By a double line
Why do covalent bonds have low melting/boiling points?
The inter-molecular forces are weak even though covalent bonds are strong
Do covalent bonds conduct electricity?
No, they’re neutral molecules and there are no charged particles to carry the current so they’re poor conductors
Which atom accepts two electrons in a dative covalent bond?
The atom that doesn’t have a full outer shell (electron-deficient)
Which atom donates two electrons in a dative covalent bond?
The atom that is donating electrons has a pair of electrons that isn’t being used Called a lone pair
How do you express a dative covalent bond?
With an arrow that points towards the atom accepting the pair
Why is it hard to break a covalent bond?
You have to put in energy to overcome the attraction in order to form a covalent bond
How do you work out the charge of a covalent bond?
Protons minus electrons
What are the types of bond in a double bond?
Sigma bond: between the nuclei of the two atoms Pi bond: second pair of electrons
What does the strength of covalent bonds depend on?
Bond length: distance between nuclei, dependent on the atomic radii, longer bonds have a weaker bond Pi bonds are weaker than sigma bonds, double bond is weaker than a single bond Pi bonds are likely to be attacked by electrophiles because the delocalisation of the electrons makes them easier to access
Do covalent bond conduct heat?
No as the molecules are not close enough to carry heat through the structure