Bond
Definition and meaning of Bond in chemistry.
A chemical bond is the strong attractive force holding two or more atoms together. This attraction creates larger structures like complete molecules, complex ions, or extended solid networks. Bonds form through the electrostatic interaction between positively charged nuclei and negative valence electrons.
In more detail
Atoms naturally seek to lower their overall potential energy by rearranging their outermost electrons. They achieve this lower energy state by forming different types of chemical bonds. In covalent bonds, nonmetal atoms share pairs of valence electrons to achieve chemical stability.
In ionic bonds, atoms completely transfer electrons to create oppositely charged atomic ions. These oppositely charged ions then strongly attract each other to form a rigid crystal lattice. In metallic bonds, valence electrons roam freely across a large network of metal cations.
The specific type of bond completely determines a substance's melting point, hardness, and chemical reactivity. Stronger chemical bonds generally result in much higher melting points and harder solid materials. Chemists accurately measure the strength of a bond using a concept known as bond energy.
Bond length describes the average physical distance between the nuclei of two bonded atoms. Bond polarity occurs when two bonded atoms share their valence electrons unequally between them. Shorter chemical bonds with higher bond orders are generally much stronger and harder to break.
Many students mistakenly believe that breaking chemical bonds releases energy into the environment. In reality, breaking any chemical bond always requires an input of outside energy. Energy is only released when new chemical bonds form during a chemical reaction.
Key facts
| Field | General Chemistry |
|---|---|
| Main bond types | Covalent, ionic, metallic |
| Key properties | Bond length, bond energy, bond polarity |
| Covalent bond nature | Sharing of valence electron pairs between atoms |
| Ionic bond nature | Complete transfer of electrons between atoms |
| Energy requirement | Breaking bonds always requires an input of energy |
In a simple hydrogen molecule (H2), two individual hydrogen atoms each contribute one valence electron. They share this electron pair to form a single nonpolar covalent chemical bond. This specific covalent bond holds the two atoms together at a perfectly stable distance. Breaking this strong hydrogen bond requires absorbing exactly 436 kilojoules of energy per mole.
Frequently asked questions
What is the main difference between an ionic and a covalent bond?
Ionic bonds transfer electrons to create charged ions, while covalent bonds share electrons between atoms.
Do chemical bonds release energy when they are broken apart?
No, breaking bonds always requires an input of energy, whereas forming new bonds releases energy.
What factors determine the overall strength of a chemical bond?
Bond strength depends heavily on the bond order, the size of the atoms, and the orbital overlap.