Introduction to Chemistry for Anatomy & Physiology: Atoms, Elements, and Mixtures

Lecture 2: Introduction to Chemistry

Overview

This section introduces foundational chemistry concepts essential for understanding Anatomy & Physiology. Topics include the nature of matter, atomic structure, elements, the periodic table, and types of mixtures found in biological systems.

Atom and Elements

Matter and Chemistry

Chemistry is the study of matter and its interactions, which is fundamental to understanding physiological processes.

• Matter is anything that has mass and occupies space.

• Matter exists in three states: solid, liquid, and gas.

• Chemistry explores the composition, structure, and changes of matter.

Atoms: The Building Blocks of Matter

An atom is the smallest unit of matter that retains its original properties. Atoms are composed of subatomic particles:

• Protons (P+): Positively charged, located in the nucleus.

• Neutrons (n0): Neutral charge, located in the nucleus.

• Electrons (e-): Negatively charged, located in electron shells surrounding the nucleus.

All atoms are electrically neutral, meaning the number of protons equals the number of electrons.

Atomic Structure

Subatomic Particles

• Protons: Define the element's identity and contribute to atomic mass.

• Neutrons: Contribute to atomic mass but do not affect charge.

• Electrons: Involved in chemical bonding and reactions.

Most of the atom's mass comes from protons and neutrons; most of its volume is empty space.

Electron Shells and Energy Levels

Electrons are arranged in energy levels (shells) around the nucleus. Each shell can hold a specific maximum number of electrons:

• First shell: up to 2 electrons (duet rule).

• Second shell: up to 8 electrons.

• Third shell: up to 18 electrons, but stable with 8 electrons (octet rule).

The octet rule states that atoms are most stable when they have eight electrons in their outermost shell.

The Periodic Table of Elements

Organization and Information

The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties.

• Atomic number: Number of protons in the nucleus.

• Atomic mass: Sum of protons and neutrons.

• Chemical symbol: One- or two-letter abbreviation for each element.

Example: Hydrogen has atomic number 1, symbol H, and atomic mass 1.0079.

Major, Mineral, and Trace Elements in the Human Body

Elements are classified based on their abundance and function in the human body.

Type	Element	Chemical Symbol	Approximate % of Body Mass
Major	Oxygen	O	65%
Major	Carbon	C	18%
Major	Hydrogen	H	10%
Major	Nitrogen	N	3%
Mineral	Potassium	K	<4%
Mineral	Sodium	Na	<4%
Mineral	Calcium	Ca	<4%
Mineral	Magnesium	Mg	<4%
Mineral	Phosphorus	P	<4%
Mineral	Chlorine	Cl	<4%
Trace	Iron	Fe	0.01%
Trace	Copper	Cu	0.01%
Trace	Iodine	I	0.01%
Trace	Zinc	Zn	0.01%

Additional info: Only a subset of trace elements is listed; others include selenium, manganese, etc.

Metals vs. Nonmetals

• Metals: Shiny, conduct electricity, found on the left side of the periodic table.

• Nonmetals: Gases or brittle solids, poor conductors, found on the right side.

Atomic Number, Atomic Mass, and Isotopes

Definitions

• Atomic number (Z): Number of protons in the nucleus.

• Atomic mass (A): Number of protons plus neutrons.

Formula:

$\text{Atomic mass} = \text{Number of protons} + \text{Number of neutrons}$

Example: Carbon has 6 protons and 6 neutrons, so its atomic mass is 12.

Isotopes and Radioactivity

Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses.

• Hydrogen has three isotopes: Hydrogen (1 proton, 0 neutrons), Deuterium (1 proton, 1 neutron), Tritium (1 proton, 2 neutrons).

• The atomic mass listed on the periodic table is a weighted average of all isotopes.

Some isotopes are radioactive and can be used in medical imaging and treatments.

Combining Matter: Mixtures

Types of Mixtures

Mixtures are combinations of two or more elements or compounds physically intermixed but not chemically bonded.

• Suspensions: Large particles are visible and settle out over time. Example: Blood cells suspended in plasma.

• Colloids: Particles are not visible, do not settle out, and the mixture appears opaque. Example: Milk, cytosol.

• Solutions: Solute particles are extremely small, not visible, and do not settle out. Example: Glucose dissolved in water.

Type	Description	Example
Suspension	Particles visible and settle out	Blood
Colloid	Opaque, particles do not settle out	Cytosol, Milk
Solution	Solute and solvent, particles do not settle out	Glucose in water

Key Terms and Concepts

• Solute: Substance dissolved in a solution.

• Solvent: Substance in which the solute dissolves; water is the most important biological solvent.

• Duet Rule: Stability with two electrons in the first shell.

• Octet Rule: Stability with eight electrons in the outer shell.

Summary

Understanding atomic structure, the periodic table, and types of mixtures is essential for studying the chemical basis of physiological processes in Anatomy & Physiology.