Interactions Flashcards
What are atoms?
An atom is a positively charged nucleus surrounded by orbiting electrons.
What is electronegativity?
Electronegativity is the property of how strongly an electron is bound to the nucleus, thus is the measure of the tendency of an atom to attract a bonding pair of electrons.
The stronger electronegativity is, the strongly the outer electrons are pulled by the nucleus; thus the atom would not easily loose electrons, but it will have a tendency to gain new ones.
- Noble elements (He, Ne, Ar): inert, since the outer shell is completely full.
- Group 17 (F, Cl, Br): high electronegative, since they have 7 electrons and need only one to have the shell full.
- Group 16 (O, S): high electronegativity, since they have 6 electrons and need two more.
- Group 15 (N): high electronegativity, since it has 5 electrons and need three more.
- Group 1 (Li, Na, K): low electronegativity, since they only have 1 electron in the outer shell and will have the tendency to loose it.
- All elements in the middle: intermediate electronegativity, since, when bonded to other elements, they will share equally the electrons.
When is a Covalent bond formed?
A covalent bond is formed when two atoms share a pair of electrons. This is due their similar electronegativity.
Carbon can form 4 covalent bonds, since it has 4 electrons and 4 spares.
When is an Ionic bond formed?
An ionic bond is the interaction of atoms that have a large difference in electronegativity. In this bond, the electron will be transferred from the atom with low electronegativity to the atom with high electronegativity. This transfer will for two ions, a cation and an anion.
Ionic bonds can be found in salt bridges and in electrostatic interactions.
What is meant with Polarity?
Polarity results from the uneven partial charge distribution between various atoms in a compound. It occurs when two atoms with intermediate difference in electronegativity interact and form a covalent bond.
The atoms in this bond will have partial charges: δ+ and δ-.
For a polar covalent bond to occur, a-symmetry of the molecule is neeed.
When do Hydrogen bonds occur?
Hydrogen bonds are electrostatic interactions between a positive partial charge (δ+) and a negative partial charge (δ-).
Hydrogen bonds can only occur between an H, that is bounded to an element of strong electronegativity (O, N, F), and an element with strong electronegativity, either O, N, F.
Since it is an interaction between partial charges, it’s very unstable and the electrons can’t be transferred within atoms.
- Intermolecular H-bond: Hydrogen bond between two molecules.
- Intermolecular H-bond: Hydrogen bond within the same molecule.
The strength of the H-bond depend on the distance between atoms and the angle at which the bond occur.
What is meant for Non-hydrogen dipole interaction?
For Non-hydrogen dipole interaction is intended all interactions that occur between two dipoles, that does not comprehend hydrogen.
When do Induced Dipoles occur?
Induced dipoles occur when an ion or a dipole induce a dipole on a neighbouring group that, per se, is not polar.
This interaction has an attractive force, called Debye force.
When London Dispersion Force occur?
The london dispersion force arises from a fluctuation of the electrons in one group that induce a transient dipole in a neighbouring group.
What are Van der Waals interactions?
Van der Waals interactions are a collection of weak, distance-dependent attractive forces between atoms and molecules.
- at very short distance, the two atoms will repulse each other.
- at long distance, the two atoms won’t sense each other.
- at intermediate distance, the two atoms will attract each other.
What is the Hydrophobic Effect?
The hydrophobic effect is the aggregation of non-polar molecules that occur spontaneously when in contact with polar molecules (such as water).
This effect is entropically favourable.
