Chemistry: Types of Chemical Bonds

Chemical Basis of Life

• Organisms are composed of matter
• Matter is anything that takes up space and has mass
• Matter is made up of elements
• Elements are substances that cannot be broken down into other substances by chemical reactions
• 92 elements exist in nature, listed in the periodic table

Learning Objectives

• Define molecules, compounds, and elements, and identify key chemical elements and their properties.
• Define isotopes and radioisotopes, providing examples of their clinical applications.
• Describe and compare ionic bonds, covalent bonds, hydrogen bonds, and Van der Waals interactions.

Elements and Compounds

• Organisms are composed of matter
• Matter is anything that takes up space and has mass
• Matter is made up of elements
• Elements are substances that cannot be broken down further by chemical reactions
• The periodic table lists the 92 naturally occurring elements

The Periodic Table

• Displays the elements, organized by atomic number and properties
• Includes a variety of elements including metals, non-metals, and metalloids.
• Elements are arranged in periods (rows) and groups (columns)
• There are other, synthetic elements not found in nature

Essential Elements of Life

• Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) make up 96% of living matter
• Other elements, including calcium (Ca), potassium (K), and sodium (Na), make up most of the remainder (4%) of living matter
• Trace elements (e.g., iron (Fe), iodine (I), selenium (Se), copper (Cu)) are needed in minute quantities for normal biological functioning

Naturally Occurring Elements in the Human Body

• Specific percentages of common elements make up the human body
• Some elements are major components
• Other elements are present in trace quantities, but are critical for proper body functioning

Trace Element Deficiencies

• Trace elements are required in small quantities but are essential for normal function.
• Deficiencies in trace elements can have significant health consequences.   - Iodine deficiency leads to goiters (enlarged thyroid glands) and hypothyroidism.   - Iron deficiency can cause iron-deficiency anemia.

Isotopes and Radioisotopes

• Isotopes are different forms of the same element with varying numbers of neutrons
  • They have different mass numbers, but the same atomic number, meaning the same number of protons
• Radioactive isotopes (radioisotopes) are unstable and spontaneously decay, emitting particles and energy
  • They are used in nuclear medicine and imaging techniques (such as PET scans)

Clinical Applications of Radioisotopes

• Used in diagnosing diseases (imaging)
• Used in treating diseases (e.g., thyroid cancer, hyperthyroidism)
• Assess severity of disease
• Monitor treatment progress

Nuclear Medicine Imaging

• Based on the use of radioactive isotopes
• Produces 3-dimensional images of functional processes in the body
• Detection of gamma rays emitted from a radioisotope

Atomic Structure

• Atoms are made up of subatomic particles: protons, neutrons, and electrons
• Protons and neutrons have roughly equal mass, while electrons have significantly less mass.
• Protons and neutrons are located in the nucleus, while electrons orbit the nucleus.
  • Electrons surround the nucleus in electron shells, the outer shell holding ‘valence’ electrons.

Atomic Number vs Mass Number

• Atomic number is the number of protons in an atom
• Mass number is the sum of protons and neutrons in an atom
• Atomic mass is approximately equal to the mass number

Isotopes

• Isotopes are different forms of an element that have the same atomic number but different mass numbers. This difference is due to variations in the number of neutrons
• Some isotopes are radioactive, spontaneously decaying to release energy and particles

Electron Configuration

• Electron configuration describes the arrangement of electrons in electron shells around the atom's nucleus
• The periodic table of elements organizes elements based on electron configuration.

Chemical Bonds

• Covalent bonds involve sharing of electrons between atoms, resulting in molecules.
• Ionic bonds involve the transfer of electrons between atoms, resulting in charged ions (anions and cations) that are held together by electrostatic attraction, forming ionic compounds
• Hydrogen bonds are weak attractions between a hydrogen atom covalently bonded to an electronegative atom (like oxygen, nitrogen, or fluorine) of one molecule and another electronegative atom of a different molecule.
• Van der Waals interactions are weak attractions between molecules or atoms that result from temporary fluctuations in electron distribution

Types of Chemical Bonds

• Strong bonds: covalent and ionic bonds
• Weak bonds: hydrogen bonds and van der Waals interactions
• The type of bond affects molecular shape and function

Chemical Reactions

• Chemical reactions involve the making and breaking of chemical bonds
  • Reactants are the starting molecules
  • Products are the resulting molecules
• Examples of chemical reactions in living organisms include photosynthesis
• The process of photosynthesis uses carbon dioxide (CO2), water (H2O), and light energy to produce oxygen (O2) and glucose (C6H12O6).

Molecules vs. Compounds

• Molecules are formed by covalent bonds, they can be formed from atoms of the same or different elements
• Compounds are formed when two or more different elements are bonded together (in fixed proportions).
• Both molecules and compounds are formed through chemical bonds.

Summary

• Key concepts from this topic include molecules, compounds, elements, isotopes, radioisotopes, and various types of chemical bonds, their properties and relative strengths.
• Students should understand how chemical bonds relate to molecular shape and function, and how these concepts are important in biological systems..