Atomic Structure and Chemical Properties

Subatomic Particles of an Atom

Atoms are composed of three main subatomic particles that determine their structure and properties.

• Protons: Positively charged particles located in the nucleus. The number of protons defines the atomic number and the element.

• Neutrons: Neutral particles also found in the nucleus. Neutrons contribute to the atomic mass but do not affect the chemical identity.

• Electrons: Negatively charged particles that orbit the nucleus in electron shells. Electrons are involved in chemical bonding and reactions.

Atomic Number and Atomic Mass

• Atomic Number: The number of protons in the nucleus of an atom. It determines the element's identity.

• Atomic Mass Number: The sum of protons and neutrons in the nucleus. It gives the approximate mass of an atom.

Isotopes

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This results in different atomic masses.

• Example: Carbon-12 and Carbon-14 are isotopes of carbon.

Valence Electrons and Chemical Bonding

Valence electrons are the electrons in the outermost shell of an atom. They determine how atoms interact and bond with each other.

• Purpose: Atoms tend to gain, lose, or share valence electrons to achieve a stable electron configuration, often resembling the nearest noble gas.

Polar and Nonpolar Molecules

• Polar Molecule: A molecule with an uneven distribution of charge, resulting in positive and negative poles. This occurs when atoms with different electronegativities share electrons unequally.

• Nonpolar Molecule: A molecule with an even distribution of charge.

• What makes a molecule polar? The presence of polar bonds and an asymmetric shape.

• Example: Water (H2O) is a polar molecule.

Inorganic Compounds

• Inorganic Compounds: Compounds that generally do not contain carbon-hydrogen bonds. Examples include water, salts, acids, and bases.

Chemical Reactions and Biochemistry

Dehydration Synthesis Reaction

Dehydration synthesis is a chemical reaction in which two molecules are joined together by removing a molecule of water.

• Example: Formation of a disaccharide from two monosaccharides.

pH Scale

The pH scale measures the concentration of hydrogen ions (H+) in a solution, indicating its acidity or alkalinity.

• Range: 0 (most acidic) to 14 (most basic), with 7 being neutral.

• Formula:

Acids, Bases, and Weak Acids/Bases

• Acid: A substance that donates hydrogen ions (H+).

• Base: A substance that accepts hydrogen ions or donates hydroxide ions (OH-).

• Weak Acid/Base: Partially dissociates in water, resulting in a mixture of ions and undissociated molecules.

Triglycerides and Lipids

• Triglyceride: A lipid molecule made of one glycerol and three fatty acids. It is the main form of stored fat in the body.

• Building Blocks of Lipids: Glycerol and fatty acids.

• Saturated vs. Unsaturated Fats: Saturated fats have no double bonds between carbon atoms; unsaturated fats have one or more double bonds.

Carbohydrates and Proteins

• Building Blocks of Carbohydrates: Monosaccharides (simple sugars, e.g., glucose).

• Building Blocks of Proteins: Amino acids.

• Three Main Types of Bonds in Proteins: Peptide bonds, hydrogen bonds, and disulfide bridges.

Vitamins Produced in the Skin

• Vitamin D: Synthesized in the skin upon exposure to sunlight (UV radiation).

Enzymes

• Enzymes: Biological catalysts that speed up chemical reactions in the body without being consumed.

• Example: Amylase breaks down starch into sugars.

Genetics and Molecular Biology

Nucleotides and Nucleic Acids

• Nucleotide: The building block of nucleic acids (DNA and RNA), consisting of a phosphate group, a five-carbon sugar (deoxyribose or ribose), and a nitrogenous base.

• DNA Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

• Base Pairing: In DNA, A pairs with T, and C pairs with G (complementary base pairing).

Hydrogen Bonds in Water and DNA

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (such as oxygen or nitrogen).

• In Water: Hydrogen bonds between water molecules give water its unique properties (e.g., high boiling point, surface tension).

• In DNA: Hydrogen bonds hold complementary base pairs together.

Location of Electrons and Protons in Atoms

• Protons: Located in the nucleus.

• Electrons: Located in electron shells/orbitals surrounding the nucleus.

Summary Table: Building Blocks of Biomolecules

Additional info: Some explanations and examples were expanded for academic completeness and clarity.