What are chemical bonds?
A chemical bond involves atoms combining to form chemical compounds and bring stability to the resulting product. In this process, atoms can share or give up electrons from their outermost shell to bond and create a new homogeneous substance.
When a chemical bond is formed, the structure and characteristics of atoms don’t change; there is only electron sharing. This means that when the chemical bond for water (H2O) is formed, for example, its elements (oxygen and hydrogen) remain the same.
The environment around us is the result of multiple chemical bonds that give matter properties, both physical and chemical. This is a product of the force generated by atoms when they combine and form bonds, given that these small particles are much more stable together than by themselves.
How does a chemical bond occur?
Every atom is composed of a core with positively charged protons and neutral neutrons, and it is surrounded by an outer layer called the electron cloud, which has a negative charge.
Opposite charges attract both within the same atom and between atoms. This attraction forms chemical bonds between different elements.
Atoms round out their electric charges by electron exchanges: they can give up, accept, or share these particles to achieve a stable electronic configuration, meaning a lower energy consumption.
What is the Lewis octet rule, and what is its relationship to chemical bonds?
American chemical physicist Gilbert Lewis devised the octet rule in 1917; it explains how atoms of different chemical elements combine to form bonds.
This theory proposes that the ions of elements on the periodic table fill their last energy levels with 8 electrons. This way, the molecules achieve stability at the level of their electronic structure.
Thus, elements with high electronegative charges gain electrons until reaching the octet, while those with low electronegativity usually lose them to achieve the same goal.
What types of chemical bonds are there?
Depending on the type of bonded atoms, which have their own characteristics and mechanisms, a chemical bond can be:
- Covalent: occurs when non-metallic atoms share electrons. In this type of bond, electrons move between atoms, producing polar covalent bonds (sharing electrons unequally) and non-polar ones (when the number of electrons is evenly distributed).
Example: water (H2O) is composed of two hydrogen atoms and one oxygen atom, and in its bond, each hydrogen atom shares an oxygen atom.
- Ionic: this occurs when metallic and non-metallic atoms bond and an electron charge is given from one to the other. As a result, both negatively charged ions (anions) and positive ones (cations) are produced, and there is an attraction between their opposite charges.
Example: in sodium chloride (NaCl), which combines a chlorine atom and a sodium atom, the former has seven electrons, and the latter has one. When forming the ionic bond, sodium gives up its electron to chlorine, thus fulfilling the octet law.
- Metallic: these are formed between atoms of metals, whose atomic nuclei gather and are surrounded by their electrons like a cloud. This is a strong kind of bond that is spread out like a network.
All pure metallic elements consist of metal bonds, for example, gold (Au), iron (Fe), aluminum (Al), etc.
What are some characteristics of chemical bonds?
- They hold atoms together inside the chemical molecules.
- The strength of a chemical bond is determined by the difference in electronegativity (the higher it is, the greater the strength of the electrons attracted between atoms.)
- Generally, the numbers of electrons are even.
- Covalent bonds can exist as a gas, solid, or liquid.
- Some covalent bonds are soluble in water, while others are in organic solvents.
- Acid covalent bonds conduct electricity in the presence of an aqueous solution (other covalent bonds are not good conductors), and ionic bonds do so when dissolved in water or melted.
- Ionic bonds have high melting and boiling points.
- Metal bonds are good conductors of heat and electricity, they’re typically in a solid state, and they are highly malleable.