Basics in Chemical Bonding

Chemical Bond

Chemical bonds are permanent links between atoms or ions that enable them to form structures such as molecules, crystals, etc.

Chemical bonds are caused by forces that attract and stabilize the constituent elements.

Octet Rule

This is a rule that if observed for every chemical bond where the valence or outer shell of electrons of an element should satisfy a number of 8 through bonding.

Types of bond

Covalent

Covalent bonds are bonds that can be described as a sharing of valence electrons to satisfy the octet rule.

This bond occurs between two nonmetals.

Ionic

Ionic bonds are described as the giving and taking of valence electrons to satisfy the octet rule.

This bond occurs between a nonmetal and a metal, where the nonmetal receive the electron and becomes an anion and the metal loses an electron and become a cation.

Metallic

These are bonds that occur between two metals; and usually is formed because the valence electrons freely move from on atom to the other, without necessarily taking or sharing them.

Lewis Symbols and Structure

Valence Electrons

These are the electrons that are involved in the formation of bonds between atoms.

Lewis Electron-Dot Structure

A simplified representation of the valence electrons of an element.

Changes in Matter

Physical Change

These are changes to the substances appearance.

Chemical

These are changes to the substances chemical composition.

Nuclear

These are changes to the substances nucleus.

Patterns in Chemical Reactivity

Combination

These are reactions where 2 or more substances ( Ex. $A$ and $B$ ) react to form a single substance ( Ex. $C$ ).

$A+B⟶C$

Decomposition

Often described as “Inverse Combination”, this involves the substance ( Ex. $C$ ) reacting to form 2 or more substances ( Ex. $A$ and $B$ ).

$C⟶A+B$

Combustion

Combustion reactions are rapid reactions that produce a flame, and commonly involve oxygen ( $O_2$ ) as a reactant.

$A+O_2⟶A{O}_2$

Single Displacement

This reaction involves one part of a reactant being displaced onto the other reactant.

$A+BC⟶AB+C$

Double Displacement

This reaction involves where one part of each reactant compounds are displaced.

$AB+CD⟶AD+CB$

Oxidation

This involves the addition of oxygen ( $O$ ) and the removal of Hydrogen ( $H$ ).

Reduction

This reaction is the reversal of the oxidation reaction. The removal of oxygen ( $O$ ) and the addition of Hydrogen ( $H$ ).

Red-Ox Reaction

This reaction is the simultaneous oxidation and reduction of the reactants.

Neutralization

These are reactions between acids and bases, which are highly reactive.

Reactions Based on Energy

Endothermic

These are reactions that involves the absorption of heat and/or energy; it often makes the surroundings colder.

Exothermic

These are reactions that involve the release of heat and/or energy; it often makes the surroundings hotter.