Introduction to Matter and Chemical Elements

Definition of Matter

Matter is anything that occupies space and has mass. All living and non-living things are composed of matter, including organisms, rocks, oceans, and air.

• Matter: Anything that takes up space and has mass.

• All matter consists of at least one chemical element.

Chemical Elements

Chemical elements are pure substances made of only one type of atom. Each element is defined by its atomic structure and properties.

• Element: The simplest unit of matter, made of only one kind of atom.

• Examples: Carbon (C), Hydrogen (H), Oxygen (O).

Atoms: The Smallest Units of Matter

Atoms are the fundamental building blocks of matter. They combine to form molecules and compounds essential for life.

• Atoms make up both elements and compounds.

• Example: Diamond (pure carbon atoms), Glucose (carbon, hydrogen, and oxygen atoms).

Atomic Structure

Subatomic Particles

Atoms are made of subatomic particles, each with a characteristic charge, mass, and location within the atom.

• Protons: Positively charged, found in the nucleus.

• Neutrons: No charge, found in the nucleus.

• Electrons: Negatively charged, orbit the nucleus.

Atomic Number and Mass Number

The atomic number is the number of protons in an atom, which defines the element. The mass number is the sum of protons and neutrons.

• Atomic Number (Z): Number of protons.

• Mass Number (A): Number of protons + number of neutrons.

Equation:

Elements of Life

Major Elements in Living Organisms

Of all known elements, only a small subset is found in living organisms. These are called the elements of life.

• CHNOPS: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur.

• Approximately 97% of the mass of most life is composed of these six elements.

• Trace elements are required in smaller amounts.

Periodic Table of Elements

The periodic table organizes all known elements based on their chemical properties.

Atomic Properties

Unique Properties of Atoms

Each atom of an element has unique properties, including atomic number, mass number, and chemical symbol.

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Number of protons plus neutrons.

• Chemical Symbol: One or two-letter abbreviation for the element.

Electron Orbitals & Energy Shells

Electron Arrangement

Electrons are arranged in energy shells around the nucleus. These shells have different energy levels and capacities.

• Shells closer to the nucleus are lower in energy.

• Valence electrons are found in the outermost shell and are important for chemical bonding.

• First shell holds up to 2 electrons; second shell holds up to 8 electrons.

Energy Shells for Key Elements

Octet Rule

Stability of Atoms

The octet rule states that atoms are more stable (less reactive) when their valence shells are fully occupied, typically with eight electrons.

• First energy shell holds up to 2 electrons.

• Second energy shell holds up to 8 electrons.

• Atoms are reactive when their outer valence shells are not full.

Application of the Octet Rule

• Example: Neon (Ne) is unreactive because its valence shell is full.

• Oxygen needs 2 more electrons to fulfill the octet rule.

Summary Table: Key Atomic Concepts

Additional info: These atomic concepts are foundational for understanding molecular interactions, chemical bonding, and physiological processes in Anatomy & Physiology. Mastery of atomic structure and element properties is essential for further study of biological molecules and cellular function.