Bonding types Flashcards
Describe a covalent molecular bond
When two non-metal atoms share their unpaired outer (valence) electrons by overlapping their electron clouds a covalent bond forms. The attraction of the two positive nuclei for the pair of shared electrons holds the atoms together. If there are a limited number of atoms in the structure it is known as a covalent molecule.
Describe a covalent network bond
When tow non-metal atoms share their unpaired outer (valence) electrons by overlapping their electron clouds a covalent bond forms. The attraction of the two positive nuclei for the pair of shared electrons holds the atoms together. If there are an unlimited number of atoms in the structure it is known as a covalent network.
Describe a metallic bond
Metal atoms have a small number of outer electrons that are free to move; this leaves positive ions in a sea of delocalised electrons (they are not attached to a nuclei). The attraction of the positive ions for the moving electrons holds the structure together and metallic bonds form.
Describe an ionic lattice bond
When metal and non-metal atoms transfer their unpaired outer (valence) electrons from the metal atom to the non-metal atom a positive metal ion and a negative non-metal ion form. The oppositely charged ions attract each other and form ionic bonds. As the ions are charged they attract each other in all directions and form giant lattice.
What does polyatomic mean?
More than two atoms
When two different elements combine, what is it that determines the type of bonds they form?
Their respective attraction for unpaired outer electrons (electronegativity)
When does a covalent bond occur?
Elements with the same or similar electronegativities (less than or equal too 0.3) will share their unpaired outer electrons equally and a covalent bond occurs
When does an ionic bond occur?
Elements with very different electronegativities (more than 1) will transfer their electrons from the element with the lower value to the one with the higher value, forming oppositely charged ions, and an ionic bond occurs
When do polar covalent bonds occur?
When you have a slight difference in electronegativity (between 0.3 and 1) there is an unequal pull on the bonding electrons resulting in a polar covalent bond.
What is a polar covalent bond?
This is where the element with the higher electronegativity pulls the bonding electrons closer to itself making it slightly negative and leaving the other element slightly positive
Is it possible to have a non-polar molecule even if the molecule contains polar bonds?
yes
How is it possible for a molecule to be non-polar despite containing polar bonds?
Give two examples of such non-polar molecules
This occurs when there are an equal number of polar bonds within the molecule and they are symmetrically opposed.
Carbon Dioxide
Carbon tetrachloride
What is required for a molecule to be polar?
Give three examples of such polar molecules
In order for a molecule to be polar it must contain at least one polar bond and if there is more than one they must be asymmetrically arraigned around the central atom
Chloromethane
Hydrogen oxide (water)
Nitrogen Hydride (ammonia)
