>編輯 Dritte JSTOR嗽 ➢
Chemical bond and its theories
A topic from the subject of Physical Chemistry in Chemistry.
Chemical Bond and its Theories
Introduction
A chemical bond is a force that holds atoms together to form molecules or crystals. It is caused by the electrostatic attraction between oppositely charged ions or the sharing of electrons between atoms.
Types of Chemical Bonds
- Ionic bonds
- Covalent bonds
- Metallic bonds
- Hydrogen bonds
Ionic Bonds
Ionic bonds are formed between atoms of metals and non-metals. In an ionic bond, one atom transfers one or more electrons to another atom. The atom that loses electrons becomes a positively charged ion, and the atom that gains electrons becomes a negatively charged ion. The oppositely charged ions are attracted to each other by the electrostatic force.
Covalent Bonds
Covalent bonds are formed between atoms of non-metals. In a covalent bond, the atoms share one or more pairs of electrons. The shared electrons are attracted to the nuclei of both atoms, and this attraction holds the atoms together.
Metallic Bonds
Metallic bonds are formed between atoms of metals. In a metallic bond, the metal atoms share their valence electrons in a sea of electrons. The valence electrons are not attached to any particular atom, and they are free to move throughout the metal. The sea of electrons holds the metal atoms together.
Hydrogen Bonds
Hydrogen bonds are formed between a hydrogen atom and an electronegative atom, such as oxygen, nitrogen, or fluorine. In a hydrogen bond, the hydrogen atom is covalently bonded to one atom and is also attracted to the electronegative atom by a dipole-dipole interaction.
Bond Theories
There are several different theories that explain how chemical bonds are formed. The most common bond theories are the valence bond theory and the molecular orbital theory.
Valence Bond Theory
The valence bond theory states that chemical bonds are formed when atomic orbitals overlap. When atomic orbitals overlap, the electrons in the orbitals can interact with each other. This interaction can lead to the formation of a chemical bond.
Molecular Orbital Theory
The molecular orbital theory states that chemical bonds are formed when atomic orbitals combine to form molecular orbitals. Molecular orbitals are orbitals that extend over the entire molecule. The electrons in molecular orbitals are attracted to the nuclei of all the atoms in the molecule, and this attraction holds the molecule together.
Experiment: Chemical Bond and Its Importance
Materials:
- Two balloons
- One cup of water
- One cup of salt
- Permanent marker
Procedure:
- Fill one balloon with air and the other balloon with water.
- Tie off the balloons.
- Label one balloon "air" and the other balloon "water."
- Add salt to the cup of water.
- Stir the water until the salt is dissolved.
- Submerge the air balloon in the water.
- Submerge the water balloon in the water.
- Draw a permanent marker line around the balloon's necks before submerging it.
- Measure the change in volume of each balloon.
Results:
- The air balloon will shrink.
- The water balloon will expand.
Conclusion:
The difference in the volume of the balloons is caused by the different types of chemical bonds that hold the atoms together in air and water. The air balloon shrinks because the atoms in air are held together by weak intermolecular bonds which are easily broken by the salt water. The water balloon expands because the atoms in water are held together by stronger covalent bonds which are not easily broken by the salt water.
This experiment demonstrates the importance of chemical bonds and their different types in determining the properties of a substance.