Structure of Atoms

Basic Atomic Structure

The atom is the fundamental unit of matter, composed of subatomic particles that determine its chemical properties and behavior.

• Matter: Anything that has mass and occupies space.

• States of Matter: Solid (e.g., bone), Liquid (e.g., blood), Gas (e.g., oxygen in lungs).

• Element: A pure substance consisting of only one type of atom, defined by its atomic number.

• Atomic Symbols: C = Carbon, H = Hydrogen, O = Oxygen, N = Nitrogen.

• Atom: The smallest unit of an element that retains its chemical properties.

Subatomic Particles

• Protons: Positively charged particles found in the nucleus.

• Neutrons: Neutral particles found in the nucleus.

• Electrons: Negatively charged particles found in orbitals around the nucleus.

Atomic Components and Location

• Nucleus: Contains protons and neutrons.

• Electrons: Located in energy levels (shells) surrounding the nucleus.

Molecules, Ions, and Compounds

• Molecule: Two or more atoms chemically bonded together (e.g., H2O).

• Compound: A substance formed from two or more different elements (e.g., NaCl).

• Ion: An atom or molecule with a net electric charge due to loss or gain of electrons (e.g., Na+, Cl-).

Chemical Bonds

Types of Chemical Bonds

Chemical bonds are forces that hold atoms together in molecules and compounds.

• Ionic Bond: Formed when electrons are transferred from one atom to another, creating ions (e.g., NaCl).

• Covalent Bond: Formed when atoms share electrons.

• Polar Covalent Bond: Electrons are shared unequally, resulting in partial charges.

• Nonpolar Covalent Bond: Electrons are shared equally.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., between water molecules).

Bond Strength

• Strongest Bond: Covalent bond.

• Weakest Bond: Hydrogen bond.

Water and Its Properties

• Characteristics of Water: High heat capacity, excellent solvent, cohesive and adhesive properties.

• Polarity: Water is a polar molecule with a slight negative charge on oxygen and a slight positive charge on hydrogen.

Acids and Bases

pH and Chemical Properties

Acids and bases are substances that alter the concentration of hydrogen ions (H+) in a solution.

• Acid: Substance that increases H+ concentration; pH < 7 (e.g., hydrochloric acid).

• Base: Substance that decreases H+ concentration; pH > 7 (e.g., sodium hydroxide).

• Neutral Substance: pH = 7 (e.g., pure water).

Organic Compounds

Elements and Types

Organic compounds are molecules containing carbon and hydrogen, essential for life.

• Main Elements: Carbon (C) and Hydrogen (H).

• Types of Organic Molecules: Carbohydrates, Lipids, Proteins, Nucleic Acids.

Polymers and Monomers

• Polymer: Large molecule made of repeating units (monomers). Example: Starch (polymer of glucose).

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically in a 2:1 ratio of hydrogen to oxygen.

• Monosaccharide: Simple sugar (e.g., glucose).

• Disaccharide: Two monosaccharides joined together (e.g., sucrose).

• Polysaccharide: Many monosaccharides linked (e.g., starch, glycogen).

• Functions: Energy source, structural support, cell recognition.

Lipids

Structure and Function

Lipids are hydrophobic organic molecules, insoluble in water, and serve as energy storage and structural components.

• Hydrophobic: Repels water.

• Examples: Cholesterol, triglycerides.

• Functions: Energy storage, insulation, cell membrane structure.

Proteins

Structure and Function

Proteins are polymers of amino acids, essential for structure, function, and regulation of tissues and organs.

• Monomer: Amino acid.

• Peptide Bond: Type of bond between amino acids.

• Enzymes: Proteins that catalyze biochemical reactions.

• Functions: Structural support (muscle, hair, nails), catalysis (enzymes), transport, defense.

Nucleic Acids

Structure and Function

Nucleic acids store and transmit genetic information.

• Examples: DNA, RNA.

• Nucleotide Components: Sugar, phosphate group, nitrogenous base.

ATP and Energy

Role of ATP

ATP (adenosine triphosphate) is the primary energy carrier in cells.

• ATP: Supplies energy for cellular processes.

• Energy Storage: The high-energy phosphate bonds in ATP store energy.

Chemical Reactions

Reactants and Products

Chemical reactions involve the transformation of reactants into products.

• Example Reaction:

• Reactants: ,

• Products:

Macromolecules Table

The following table summarizes the main macromolecules, their elements, monomers, and examples.

Additional info:

• Enzymes are biological catalysts that speed up chemical reactions without being consumed.

• Denaturation of proteins can occur due to changes in temperature, pH, or chemical exposure.

• Water's polarity and hydrogen bonding make it essential for life, influencing properties like cohesion, adhesion, and solvent ability.

• pH is defined as .