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CHEMICAL BONDS

1.Define

Electron affinity

• The energy released when an electron is added to neutral gaseous atom, is known as electron affinity.

1. cations and anions

• When an atom loses electron it becomes cation, and when an atom gains electrons it becomes anion.

coordinate bond

• A coordinate bond is a type of covalent bond formed by the donation of a lone pair of electrons by one atom.

2 List four properties of ionic  and covalent compounds

Ionic Bond

• The transfer of electrons from one atom to another leads to the formation of the chemical bond. This bond is known as an ionic bond.
• An ionic bond is formed in two scenarios:
• When one of the atoms donates electrons to achieve the inert gas electron configuration for the completion of octet resulting in stability.,
• When the other atom needs electrons to achieve the inert gas electron configuration.
• So, when a metal reacts with a non-metal, transfer of electrons takes place from metal atoms to the non-metal atoms, and thus an ionic bond is formed.
• The strong force of attraction developed between the oppositely charged ions is known as an ionic bond. Examples of ionic bonds are sodium chloride, magnesium chloride and magnesium oxide, etc.
• Ionic compounds are held strongly by the electrostatic force of attraction because oppositely charged ions are present.

b.Properties Of Ionic Compounds

• Physical properties of ionic compounds:
  • Ionic compounds are solids and are hard to break due to the strong force of attraction between the positive and negative ions.
  • However, they break into pieces when pressure is applied. So they are considered brittle.
• Melting and boiling points of ionic compounds:
  • A large amount of energy is required to break the ionic bonds between the atoms.
  • So, they have high melting and boiling points.
• Solubility of ionic compounds:
  • Ionic compounds are generally soluble in polar solvents such as water but the solubility tends to decrease in non-polar solvents such as petrol, gasoline etc.
• Conduction of Electricity:
  • Although ionic compounds do not conduct electricity in the solid state because movement of ions is not possible.
  • But they are good conductors in a molten state because electrostatic forces of attraction between the ions are overcome by the heat released.

c.Covalent Bond

• Whenever a non-metal combine with another non-metal, sharing of electrons takes place between their atoms, which leads to the formation of a covalent bond. A covalent bond can also be formed between two atoms of the same non-metal.

Covalent compounds are formed by the sharing of electrons between atoms. Such compounds are known as covalent compounds.

d.Properties Of Ionic Compounds

• They are usually crystalline solids.
• They have high melting points and high boiling points.
• They are usually soluble in water but insoluble in organic solvents.
• They conduct electricity when dissolved in water or when melted.

3. What property determines the polarity of a covalent bond?

Polarity in a bond results from an uneven sharing of electrons. An extreme example is an ionic bond, in which an electron is almost fully transferred from one atom to another due to the second atom’s electron affinity.

In order to generate an uneven pull on shared electrons, the atoms involved in the bond must have significantly differing electronegativities. This will cause one atom to pull electrons closer to its nucleus, away from the other atom involved.

Molecular and electronic geometry can affect the polarity of a compound, but do not directly affect polarity of a single given bond. Atomic radius does not play a significant role in polarity.

4. Differences Between Ionic Compounds And Covalent Compounds

5.  Ammonia is an important compound used by industry and agriculture.

Ammonia is an important compound used in various industries and agriculture as discussed below

• Fertilizer Production:Ammonia is a primary component in the production of nitrogen-based fertilizers. It is used to synthesize ammonium nitrate, urea, and other nitrogen-rich compounds. These fertilizers provide essential nutrients, particularly nitrogen, to promote plant growth and increase crop yields.
• Industrial Chemicals: Ammonia is a versatile chemical used in the production of various industrial compounds. It serves as a precursor for the synthesis of numerous chemicals, including nitric acid, hydrogen cyanide, acrylonitrile, and various plastics, resins, and dyes. These chemicals find applications in industries such as pharmaceuticals, textiles, plastics, and explosives.
• Refrigeration and Cooling: Ammonia is widely used as a refrigerant in industrial refrigeration systems, cold storage, and food processing facilities. Its excellent thermodynamic properties, including high cooling capacity and low environmental impact, make it a preferred choice in large-scale refrigeration applications.
• Water Treatment:Ammonia is used in water treatment processes, particularly for disinfection and removal of impurities. It can react with chlorine to form chloramines, which are effective disinfectants for treating drinking water and wastewater. Ammonia is also used to control pH levels in water treatment systems.
• Cleaning Agents:Ammonia-based cleaning agents are commonly used for household cleaning purposes. They are effective for removing stains, grease, and grime from various surfaces. However, it’s important to use ammonia-based products with caution and follow proper safety guidelines due to its potential irritant properties.
• Textile and Fiber Industry: Ammonia is utilized in various stages of textile and fiber production. It is involved in processes such as scouring, bleaching, and dyeing of fabrics. Ammonia helps in removing impurities, improving colorfastness, and enhancing the overall quality of textile products.
• pH Control:Ammonia is used to adjust and control pH levels in various applications. It can act as a buffering agent, helping to maintain the desired pH range in solutions and processes.

• a) Describe, in terms of outer shell electrons, the bonding in a molecule of ammonia. You should include a suitable diagram showing outer shell electrons in your answer.
• three single bonds from nitrogen to hydrogen atoms
• non-bonded pair of electrons left on nitrogen

b) Explain why ammonia is a gas at room temperature.

• Because of weak forces between ammonia molecules  which cause the molecules  to have sufficient energy at room temperature to overcome these forces

5. Lithium chloride is a solid with a high melting point. It conducts electricity only when molten or in solution. Describe the bonding present in lithium chloride and explain the properties given above.

• lithium atom loses an electron
• it becomes a positive ion
• chlorine atom gains an electron
• it becomes a negative chloride ion
• diagram showing transfer of electrons from lithium to chlorine
• strong force of attraction between oppositely charged ions
• high melting point due to strong bonds between ions
• conducts electricity when molten or in solution as charged ions are free to move
• does not conduct when solid as ions are not free to move

5. Ammonia, NH₃, is a compound that contains the elements nitrogen and hydrogen. The electronic structure for each element is given below.

                  N = 2, 5    H = 2, 1

State which of the following dot and cross diagrams represents the bonding in a molecule of ammonia.