Chemistry Basics: Matter and Atoms

Matter and Chemistry

• Matter is defined as anything that has mass and occupies space.
• Chemistry is the scientific study of matter and its interactions.

Atoms and Elements

• An atom is the smallest unit of matter that retains its properties.
• Electron shells: 1st shell holds 2 electrons, 2nd shell holds 8, and 3rd shell can hold up to 18 but is satisfied with 8.
• An element cannot be broken down into simpler substances by chemical means.
• Elements are categorized by atomic number, which is the number of protons.
• The periodic table lists elements by chemical symbols, typically derived from the element’s name (e.g., H for Hydrogen).

Elements in the Human Body

• Major elements:
  • Oxygen: 65%
  • Carbon: 18%
  • Hydrogen: 10%
  • Nitrogen: 3%
  • Minerals: 4%

Isotopes

• Isotopes have the same atomic number but different mass numbers.
• Some isotopes are unstable and release energy, which is utilized in nuclear medicine.
• Common applications include cancer therapy, radiotracers, and thyroid treatment.

Mixtures and Solutions

• A mixture consists of atoms from two or more elements that are physically intermixed.
• A solute is the substance that dissolves, while the solvent is the substance that dissolves the solute, with water being the most important solvent in the human body.
• Concentration is the amount of solute in a solution (e.g., 10% salt solution = 10g salt in 100mL water).

Molecules and Compounds

• A molecule is formed by chemically bonded atoms, while a compound consists of two or more different elements (e.g., H2O).

Chemical Bonds

• Ionic bonds occur when electrons are transferred between a metal atom (e.g., Sodium) and a nonmetal atom (e.g., Chlorine).
• Ions are charged particles; cations have a positive charge and anions have a negative charge.
• Covalent bonds occur when atoms share electrons.

Activation Energy and Reaction Rates

• Activation energy is required for chemical reactions to occur, allowing atoms to collide with sufficient force.
• Factors affecting reaction rates include concentration, temperature, reactant properties, and catalysts, which lower activation energy.

Enzymes

• Enzymes are biological catalysts that speed up reactions without being permanently altered.
• They are specific to substrates and do not change the overall chemical reaction.

Properties of Water

• Water absorbs heat and changes from liquid to gas, carrying heat with it.
• Acts as a cushion, lubricant, and is known as the universal solvent due to its ability to dissolve many substances.
• Hydrophilic solutes are water-loving (can dissolve in water), while hydrophobic solutes do not (e.g., oils, fats).

Acids, Bases, and pH

• Acids donate hydrogen ions (H+) in solution, increasing H+ concentration.
• Bases are hydrogen ion acceptors, decreasing H+ concentration.
• The pH scale ranges from acidic (less than 7, high H+ concentration) to basic (greater than 7, low H+ concentration).
• Each unit change in pH reflects a tenfold change in H+ concentration.

Buffers

• Buffers are chemical systems that resist changes in pH and are made up of a weak acid and its corresponding base.

Proteins

• Proteins play essential roles: structural (hair, nails), functional (enzymes), and as energy sources.
• Made up of amino acids, which possess a core structure including carbon, hydrogen, oxygen, and nitrogen.
• Amino acids join to form peptides (e.g., dipeptides consist of two amino acids).

Protein Structure

• Fibrous proteins consist of long strands and are primarily made of nonpolar amino acids, found in connective tissues.
• Globular proteins are spherical and perform roles such as enzymatic and hormonal functions.
• Protein structures have four levels of complexity.