Electronegativity Flashcards
Describe the trend in electronegativity on the periodic table:
Electronegativity increases as the groups go along but as the periods decrease.
Which element has the highest electronegativity?
Helium.
What are non-polar bonds?
When the bonded electron pair is shared equally.
Why does HCl form polar molecules? (2)
-Cl is more electronegative than H, this means the electron cloud is distributed unevenly
-HCl is an asymmetrical molecule so the dipoles do not cancel
What is a polar bond?
A bond in which there is an uneven distribution of electrons.
Why can a molecule with polar bonds end up being a non-polar molecule?
If the molecule is symmetrical then the dipoles will cancel each other out and there will be no overall permanent dipole.
How do you know if a molecule is symmetrical?
All the atoms around the central atom are the same and there are no lone pairs on the central atom.
How do you know if a molecule is asymmetrical?
The central atoms has two or more different atoms or the central atom has one or more lone pairs.
What are the 3 types of intermolecular forces?
- Hydrogen bonding
- Permanent dipole-dipole forces
- London forces
What do London forces occur between ?
Non-polar molecules.
What are London forces?
They are temporary, induced dipole-dipole forces.
Do London forces act for a long or short time?
Why?
A short time, as the electron density is constantly changing.
What are the weakest intermolecular forces?
London forces.
