3.1.3.2 Covalent bonding Flashcards
What is a covalent bond?
-covalent bonds occur between two non-metals
-it involves the sharing of outer electrons between two or more atoms
-it means that both atoms can achieve a noble gas structure and become stable (full outer shell).
-no electrons are transferred
Why do simple covalent structures have low melting and boiling points, and aren’t strong?
There are many weak intermolecular forces of attraction between molecules which require little energy to overcome.
What are the bonds called that hold simple covalent structures together?
Weak intermolecular forces of attraction
Why do simple covalent structures not conduct electricity?
There are no free ions or electrons in the structure so no particles free to carry electrical charge through the structure.
What is a giant covalent structure?
Large structures of non-metals bonded via strong covalent bonds
What are the general properties of giant covalent structures?
-solid at room temperature
-high melting points and boiling points
Why do giant covalent structures have high melting points and boiling points?
They have many strong covalent bonds which require lots of energy to overcome.
What are the properties of silicon dioxide?
-high melting point and boiling point
-similar structure to diomand
What are the properties of diomand?
-4 strong covalent bonds per carbon atom
-very hard
-high melting point and boiling point
-does not conduct electricity as no delocalised electrons to carry electrical charge.
What are the properties of graphite?
-each carbon atom forms 3 strong covalent bonds
-soft material due to weak intermolecular forces of attraction between layers allow leathers to slide over each other, which need little energy to overcome
-high melting point and boiling point
-good electrical conductor as each carbon atom forms 3 strong covalent bonds so one delocalised electron per carbon atom is free to move around the structure and carry electrical charge.
Describe the structure and properties of buckminsterfullerene
-an allotrope of carbon so made up of carbon atoms only
-a simple molecular structure
-does not conduct electricity as all electrons are in covalent bonds so np free electrons to carry electrical charge through the structure
-low melting and boiling points due to weak van der waals forces between layers which require little energy to overcome.
What is a dative covalent bond?
A covalent bond that is formed when both electrons in a shared pair of electrons originate from one atom. Once formed, this bond is no different from any other covalent bond.
What is a lone pair of electrons?
A pair or electrons in the outer shell that are not already involved in a bond.
