Structure And Bonding Flashcards
Describe pure covalent bonding
The shared pair of electrons is shared equally by the atoms in the molecule
Describe polar covalent bonding
Unequal sharing of the bonded electrons. Which causes one atom to have a slightly negative charge, and the other having a slightly positive charge
What do polar covalent bonds create?
Permanent dipoles
Explain electronegativity
A numerical measurement on a scale of 0-4 (low to high) used to sssess an elements ability to attract bonded electrons
What does the difference in electronegativity between atoms in a compound show?
An indication of the type of bonding present
Describe the bonding continuum
The type of bonding changes gradually as the difference in electronegativity between atoms increases
What is at either ends of the bonding continuum?
Ionic bonding at one end and pure covalent bonding at the other
What is in the middle of the bonding continuum?
Polar covalent bonding
What are intermolecular forces, and what is the other name they are known by?
Act between molecules, known as van der waals forces
Name the three types of van der waals forces
London dispersion forces
Permanent dipole- permanent dipole interactions
Hydrogen bonding
Describe London dispersion forces
Weak attractions between temporary dipoles in molecules, and are significant between non-polar molecules
Describe permanent dipole-permanent dipole interactions.
Attractions between polar molecules which have permanent dipoles
When will a molecule only be polar?
If one side of the molecule is slightly positive and the other is slightly negative
When do hydrogen bonds form?
Form between highly polar molecules which have hydrogen bonded to the greatly electronegative elements
What’s are the highly electronegative elements that allow for hydrogen bonds when they are bonded with hydrogen?
Fluorine
Oxygen
Nitrogen
What does hydrogen bonds give compounds that is unusual?
Unusually high melting and boiling points
Why do hydrogen bonding give unusually high melting and boiling points?
Because they are the strongest van der waals forces so they need more energy to separate the molecules
An example of hydrogen bonding?
Water
When water is cooled to 4 degreees Celsius what happens?
It expands and decreases density
Why does water expand and decrease density when cooled?
The water molecules form a more open structure with increased hydrogen bonding
Compounds with molecules and which have hydrogen bonds between them are more viscous than?
Compounds with molecules which have other intermolecular forces
The polar nature of water makes it a good solvent for what type of compounds?
Ionic and polar covalent compounds
Non-polar solvents can dissolve what type of substances?
Non-polar substances
The molecules of polar covalent liquids which are miscible with water form hydrogen bonds with?
Water molecules
