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Chemistry of Life

Introduction to Elements and Compounds

• Living Organisms: Composed of matter, which is made of chemical elements.

• Essential Elements: About 25 elements are essential for human life.

• Dominant Elements: Four elements—oxygen (O), carbon (C), hydrogen (H), and nitrogen (N)—account for 96% of the weight of most living organisms.

• Compounds: Substances consisting of two or more different elements in a fixed ratio.

Elements in the Human Body

• Table of Elements

  • Oxygen (O): 65% of body weight (including water)

  • Carbon (C): 18.5%

  • Hydrogen (H): 9.5%

  • Nitrogen (N): 3.3%

  • Calcium (Ca): 1.5%

  • Phosphorus (P): 1.0%

  • Trace Elements (less than 0.01%): Includes Boron (B), Chromium (Cr), Cobalt (Co), Copper (Cu), and others.

Atoms and Subatomic Particles

• Definition of Atoms: An atom is the smallest unit of matter that retains the properties of an element.

• Subatomic Particles:

  • Protons: Positively charged, found in the nucleus.

  • Neutrons: Electrically neutral, also in the nucleus.

  • Electrons: Negatively charged, orbit the nucleus.

• Atomic Number: Unique number of protons defines the element.

Isotopes

• Definition: Atoms of the same element that have different mass numbers due to varying neutron counts.

• Chemical Behavior: Isotopes behave identically in chemical reactions.

• Radioactive Isotopes: Nucleus decays spontaneously, emitting particles and energy.

Types of Chemical Bonds

• Covalent Bonds: Atoms share electrons.

  • Non-Polar Covalent: Equal sharing of electrons.

  • Polar Covalent: Unequal sharing, leading to charged regions.

• Ionic Bonds: Formed through the transfer of electrons, resulting in charged ions which attract each other.

• Hydrogen Bonds: Weak bonds formed between a partially charged hydrogen atom and another charged substance.

Chemical Reactions

• Rearrangement of Matter: Involves breaking and forming bonds.

• Water Formation: Example of a chemical reaction converting reactants to products.

• Conservation of Matter: Chemical reactions do not create or destroy matter.

Properties of Water

• State of Matter: Water exists as gas, liquid, and solid.

• Solvent Properties: Excellent solvent due to polarity.

• Cohesion and Adhesion: Water molecules stick to each other (cohesion) and to other charged substances (adhesion).

  • Capillary Action: The ability of water to rise against gravity due to cohesion and adhesion.

• Surface Tension: Water molecules at the surface are held together tightly, allowing small objects to sit on the surface.

• Ionization: Water can dissociate into H+ (acid) and OH- (base).

Acidity and Basicity

• pH Scale: Measures acidity and basicity based on H+ ions concentration.

  • Acidic: Higher H+ concentration (0-6 on the scale)

  • Neutral: Equal H+ and OH- concentration (pH 7)

  • Basic: Higher OH- concentration (8-14 on the scale).

Molecular Diversity and Organic Compounds

• Carbon's Versatility: Carbon can bond with four other atoms, forming diverse organic compounds.

• Isomers: Molecules with the same formula but different structures.

• Functional Groups: Specific groupings of atoms within molecules that have characteristic properties.

  • Examples: Hydroxyl, carbonyl, carboxyl, amino, phosphate, methyl groups.