1. a)Differentiate between valency and oxidation number
b)Write the valency and oxidation numbers of the following elements: Na, Mg, Ba,
Co, Ni, S, C, Si, Cl, Al
2. State how electronegativity, first ionization energy and standard electrode potential
contribute to bonding.
3. Explain the types of bonding blow using examples
• Ionic bonding
• Covalent bonding
• Metallic bonding
• Van der waals force
• Hydrogen bonding
4. What are minerals and state examples of minerals formed through
• Ionic bonding
• Covalent bonding
5. Why is silica important when we talk about earth’s crust? Name the common groups of
silicate and briefly state their compositions.
1. a) Valency refers to the combining capacity of an element, which is determined by the number of electrons it needs to gain, lose or share in order to achieve a full outer shell. Oxidation number, on the other hand, is the charge that an atom would have if the shared electrons were divided equally between the atoms in a compound.
b) Valency and oxidation numbers of the elements:
- Na: Valency 1, Oxidation number +1
- Mg: Valency 2, Oxidation number +2
- Ba: Valency 2, Oxidation number +2
- Co: Valency 2, Oxidation number +2
- Ni: Valency 2, Oxidation number +2
- S: Valency 2, Oxidation number -2
- C: Valency 4, Oxidation number +4
- Si: Valency 4, Oxidation number +4
- Cl: Valency 1, Oxidation number -1
- Al: Valency 3, Oxidation number +3
2. Electronegativity, first ionization energy, and standard electrode potential contribute to bonding by determining how likely an atom is to attract or lose electrons in a chemical reaction. Electronegativity affects the type of bonding that occurs, with a large electronegativity difference leading to ionic bonding, while a small difference leads to covalent bonding. First ionization energy determines how easily an atom can lose an electron to form a positively charged ion, while standard electrode potential measures the ability of an atom to attract electrons in a chemical reaction.
3. Types of bonding:
- Ionic bonding: Involves the transfer of electrons from one atom to another, creating ions with opposite charges that attract each other (e.g. NaCl).
- Covalent bonding: Involves the sharing of electrons between atoms to achieve a full outer shell (e.g. H2O).
- Metallic bonding: Involves the delocalization of electrons within a metal lattice, creating a "sea" of electrons that hold the metal atoms together (e.g. copper).
- Van der Waals force: Weak intermolecular forces that hold molecules together, including London dispersion forces, dipole-dipole interactions, and hydrogen bonding (e.g. between noble gases).
- Hydrogen bonding: A specific type of dipole-dipole interaction where a hydrogen atom is covalently bonded to a highly electronegative atom (e.g. H2O).
4. Minerals are naturally occurring inorganic solids with a definite chemical composition and a crystal structure. Examples of minerals formed through:
- Ionic bonding: Halite (NaCl)
- Covalent bonding: Diamond (C)
5. Silica is important in the earth's crust because it is one of the most abundant minerals and plays a crucial role in the formation of rocks and minerals. Common groups of silicate minerals include:
- Nesosilicates: Composed of isolated silicate tetrahedra (e.g. olivine)
- Sorosilicates: Composed of pairs of silicate tetrahedra sharing oxygen atoms (e.g. epidote)
- Cyclosilicates: Composed of rings of silicate tetrahedra (e.g. beryl)
- Inosilicates: Composed of chains of silicate tetrahedra (e.g. pyroxene)
- Phyllosilicates: Composed of sheets of silicate tetrahedra (e.g. mica)
- Tectosilicates: Composed of a three-dimensional network of silicate tetrahedra (e.g. quartz)