topic 6- covalent bonding Flashcards
What are covalent bonds?
When two non-metal atoms share a pair of electrons
An example of a small covalent molecule
Water
An example of a large covalent molecule
Polymers such as silk and polyester
An example of a giant covalent structure
Diamond
Nitrogen atoms have 5 electrons in the outer shell. What type of bond forms between two nitrogen atoms?
Triple covalent bond
How do we know how many electrons are on the outer shell of an element?
The amount of electrons in the outer shell is the same as the element’s group number
How do we work out how many covalent bonds an atom can form?
Outer shell number- group number
Simple molecular substances usually have ____ melting and boiling points
Low
What states are simple molecular substances generally at room temperature?
Gas or liquid
Why do simple molecular substances have low melting and boiling points?
There are intermolecular forces between simple molecules. These intermolecular forces are much weaker than the strong covalent bonds in molecules. When simple molecular substances melt and boil, it is the weak intermolecular forces that are overcome. The covalent bonds ARE NOT BROKEN. Very little energy is required to overcome the intermolecular forces, so simple molecular substances usually have low melting or boiling points.
A substance can conduct electricity if…
- it contains charged particles AND
- these particles are free to move from place to place
Why do simple molecules not conduct electricity?
Simple molecules have no overall charge, or charged particles that can separate, so simple molecular substances cannot conduct electricity, even when liquid or dissolved in water. + they don’t contain delocalised electrons
Which diatomic element has a triple covalent bond?
Nitrogen
Bigger molecules usually have ____ melting and boiling points
higher
Small covalent molecules are held together by strong _____ (found within molecules) covalent bond
Intramolecular
