Electronegativity, Polarity, Ionic radius - Chapter 8

Chemical bond

An interaction that forms between two atoms. The electrons of each atom are attracted by the positive nucleus of the opposite atom. This stabilizes both atoms.

Reasons for bonding

It stabilizes both atoms, such that they are both in a lower energy state

Bond energy

The amount of energy required to break a bond between two atoms

Bond length

The distance between the nucleus of two atoms joined in a bond. Stabilization is maximized and repulsion between the protons is minimized.

Electronegativity

The ability of an atom in a molecule to attract shared electrons to itself

Trend for electronegativity across a period

Electronegativity increases (excluding noble gases) as the atoms get closer to the noble gas electronic configuration

Trend for electronegativity down a group

Electronegativity decreases as the electrons involved in bonding are further away from the nucleus so less stability is gained

Ionic bond

Formed when a nonmetal and a metal are joined together. The difference in electronegativity between the two atoms is large.

Covalent bond

Formed when two nonmetals are joined together. The difference in electronegativity between the two atoms is small.

Polar bond

When the more electronegative atom is slightly negative while the other atom is slightly positive

Nonpolar bond

When the two atoms have the same electronegativity

Dipole

Two poles with one end positive and the other negative

Electrons in covalent compounds

Atoms share electrons so that they each have a noble gas configuration

Electrons in ionic compounds

Metals will give electrons to nonmetals so that they have a noble gas configuration

Isoelectronic species

Anions and cations which have the same number of electrons

Model

Used to explain many phenomenon. Often simplified versions of what happens at the microscopic level but allows for a practical approach at the macroscopic level. Evolves from observations and allows us to make predictions. Many assumptions are involved.

Localized Electron Bonding Model (LE model)

States that a molecule (covalent compound) is composed of atoms which are bound together by sharing pairs of electrons. Electrons involved in the formation of atoms are called bonding pairs. Electrons localized on an atom are called lone pairs.

Three main parts of the LE model

Description of the valence electron arrangement using Lewis structures, prediction of the geometry of the molecule using the VSEPR model, description of the type of atomic orbitals used to share electrons or hold lone pairs

Limitations of LE model

Species with odd numbers of electrons cannot be analyzed with the model because we consider all electrons as pairs