Elements combine with one another inorder to attain stable electronic configuration. Rare gases are stable owing to their electronic configuration, hence inorder to achieve stable duplet of octet configuration state, elements undergo chemical combination.

There are two main types of chemical combination

1. Electrovalent or ionic combination
2. Covalent combination

An electrovalent combination, also known as ionic bonding, occurs when atoms transfer electrons to achieve a stable, full outer electron shell. This typically involves a metal atom, which donates electrons, and a non-metal atom, which accepts electrons. The resulting electrostatic attraction between the positively charged metal ion (cation) and the negatively charged non-metal ion (anion) forms an ionic compound.

For example, in sodium chloride (NaCl), sodium (Na) donates an electron to chlorine (Cl), forming Na⁺ and Cl^- ions that attract each other to create the salt NaCl. Other examples include: sodium hydroxide, calcium oxide, potassium chloride, etc.

1. High melting and boiling points due to strong ionic bonds.
2. Solubility in water and polar solvents, as ions can be separated and interact with water molecules.
3. They conduct electricity in molten or aqueous form, as ions can move and carry an electric charge.
4. They are solids at room temperature
5. Formation of crystalline structures in solid state.
6. Electrolytic dissociation into ions when dissolved or melted.
7. They do not dissolve in non-polar solvents like benzene.
8. Ionic compounds do not form molecules.

In this type of combination, electrons are shared and not donated. It usually involves non-metals. Covalent combination is divided into

1. Ordinary covalent combination
2. Coordinate covalent combination or dative bonding

Covalent combination involves the sharing of electrons between atoms to achieve a stable electron configuration. This bonding occurs primarily between non-metal atoms. Each atom contributes one or more electrons to a shared pair, forming a covalent bond. The resulting molecule is held together by the shared electrons, creating a stable structure.

For example, in a water molecule (H₂O), two hydrogen atoms share electrons with an oxygen atom, forming covalent bonds and completing the outer electron shells of both hydrogen and oxygen. Other examples include the combination to form CO₂, NH₃, H₂, SO₂

Dative bonding, also known as coordinate covalent bonding, occurs when one atom donates a pair of electrons to another atom. Unlike regular covalent bonds where electrons are shared, in dative bonding, one atom provides both electrons for the shared pair. This often involves a Lewis acid-base interaction, where the Lewis acid (electron acceptor) receives electrons from the Lewis base (electron donor).

An example of dative bonding is found in the ammonium ion (NH₄⁺), where a nitrogen atom donates a pair of electrons to a proton (H⁺), forming a coordinate covalent bond. Other examples include the formation of oxonium ion (H₃O⁺)

1. Low melting and boiling points
2. Generally poor conductors of electricity
3. Exist as gases, liquids, or soft solids at room temperature
4. Often have lower solubility in water
5. Form molecules with distinct shapes and sizes
6. Typically have lower density compared to ionic compounds
7. Share electrons between atoms

These are weak intermolecular forces existing between discrete molecules. They are important in the liquefaction of gases and the formation of molecular lattice as in iodine and naphthalene crystals.

Van der Waals forces are weak attractive forces that exist between molecules as a result of temporary fluctuations in electron distribution. These forces include three main types:

1. London Dispersion Forces: Also known as instantaneous dipole-induced dipole forces, these arise from the temporary imbalance of electron distribution in a molecule, creating a transient dipole moment that induces a dipole in a neighboring molecule, leading to an attractive force between them.
2. Dipole-Dipole Interactions: Occur between polar molecules with permanent dipole moments. The positive end of one molecule attracts the negative end of another, resulting in an attractive force.
3. Hydrogen Bonding: A specific type of dipole-dipole interaction that occurs when a hydrogen atom is bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) and forms a strong interaction with a lone pair of electrons on another electronegative atom. Hydrogen bond is strongest in hydrogen fluoride. Hydrogen bond is responsible for hight boiling point in alkanols and organic acids.

Metallic bonding is a type of bonding found in metals where positively charged metal ions are held together by a sea of delocalized electrons. This electron "sea" allows for high electrical conductivity, malleability, and ductility in metals.

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