Importance of Atoms

• All matter is composed of atoms.
• Atoms are the fundamental building blocks of everything.

Basic Structure of Atoms

• Components: protons, neutrons, electrons.
• Nucleus contains protons (p, +1 charge) and neutrons (n, 0 charge).
• Electrons (e-, -1 charge) orbit the nucleus in energy levels.

Elements and Compounds

• Elements consist of one type of atom.
• Compounds are combinations of different elements in specific proportions.

Chemical Bonding

• Atoms bond to fill outer energy levels.
• Types of bonds:
  • Covalent (sharing electrons)
  • Ionic (transferring electrons)
• First energy level can hold 2 electrons, subsequent levels can hold 8.

Electronegativity

• Measure of an atom's ability to attract electrons.
• Electronegativity values:
  • C = 2.5, H = 2.1, O = 3.5, N = 3.0.

Covalent Bonds

• Formed between non-metals.
• Can be polar (unequal sharing) or non-polar (equal sharing).
• Electronegativity difference influences sharing.

Bond Characteristics

• Non-polar: equal sharing of electrons.
• Polar covalent: unequal sharing leading to slight charges.
• Ionic: typically involves a metal and has a large electronegativity difference.

Examples of Bond Types

• Determine the type based on electronegativity difference:
  • O2: Non-polar (DEN = 0)
  • CrO: Ionic (DEN = 1.9)
  • Br2: Non-polar (DEN = 0)
  • H2O: Polar (DEN = 1.4)
  • CH4: Non-polar (DEN = 0.4)
  • KCl: Ionic (DEN = 2.2)
  • CH3F: Polar (DEN = 1.5).

Ionic Bonds

• Formed between ions resulting from electron transfer.
• Ions are charged entities due to the gain or loss of electrons.
• In water, ionic compounds dissociate into their ions.

Radioisotopic Labelling

• Used in nuclear medicine to visualize internal organs.
• Radioactive compounds are injected for diagnostic imaging in conditions like cancer.