Polar molecules show Keesom forces. Polar molecules have heteroatoms that differ in electronegativity values such that the electronegativity difference between the two atoms in a polar covalent bond is greater than 0.5 but less than 1.7. For example, HF, HCl, R-OH, etc.
London Dispersion forces are seen in all the atoms and the molecules; however, it is the exclusive force binding nonpolar molecules. Nonpolar molecules are made of two or more atoms, and the electronegativity between two atoms in a covalent bond is less than 0.5. Therefore, no charges are separated to create poles in nonpolar molecules or atoms. Despite not having poles, nonpolar molecules interact using a weak force of attraction known as the London Forces.
Learning Objective: To study the nucleophiles that function as sigma bond donors that form Carbon, Hydrogen, and Halogen bonds with the substrate.
Prerequisites:
Electronegativity trend of the elements from the Periodic table
Learning Objective: To study the three types of addition reactions that nucleophiles undergo.
Skill Level - Intermediate
Prerequisites:
A metallic bond is a chemical bond seen in metals consisting of tightly bound metal atoms of the same type.
Metals are large atoms that do not firmly hold their outermost valence electrons and easily lose them. Once the electrons are lost, the metal atoms become positively charged, called kernels. The position of these kernels is fixed to avoid repulsions and is part of the solid structure.
Radicals | Electrophiles |
|---|---|
Free Radicals are the by-product of homolytic bond cleavage. | Electrophiles are the by-product of heterolytic bond cleavage. |
The two-electron bond breaks in half, dividing the electrons equally between the two atoms to form two free radicals. Therefore, free radicals are atoms or molecules carrying a single electron. |
A nonpolar molecule is made of two or more atoms where the electronegativity difference between the atoms is less than 0.5. Therefore, the electron density in the bond is equally distributed, and there is no concentration of electrons on one atom to create a charge separation rendering the molecule essentially without poles or nonpolar. Such nonpolar molecules like H2, CH4, He, etc., will interact using the London dispersion forces without forming any positive or negative pole.
The random collisions of the colloidal particles (dispersed phase) with molecules of the dispersion medium (colloidal sol) that results in a zig-zag movement of the colloidal particles, when observed under an ultramicroscope, is known as the Brownian Motion.
Curly Arrows - the curved and barbed arrows you might have seen in reactions have been the language of organic chemistry for over 100 years.
Fundamentally, the arrows represent the path of the electrons. The way they hop between atoms dictates whether a bond will form or break, causing those miraculous molecular transformations.