Fundamentals of General, Organic, and Biological Chemistry - Chapter Two

Chapter Two: Atoms and the Periodic Table

• Textbook: Fundamentals of General, Organic, and Biological Chemistry

• Edition: 8th Edition

• Chapter: Chapter Two

• Topic: Atoms and the Periodic Table

Chapter Two: Atoms and the Periodic Table - Textbook: Fundamentals of General, Organic, and Biological Chemistry - Edition: 8th Edition - Topic: Atoms and the Periodic Table

2.1 Atomic Structure

1. Subatomic Particles

   • Protons ($p^+$): Positively charged particles, located in the nucleus. Their number determines the element (atomic number).

   • Neutrons ($n^0$): Neutral particles with no charge, located in the nucleus. They contribute to the atomic mass.

   • Electrons ($e^-$): Negatively charged particles, moving rapidly in the space surrounding the nucleus. Their mass is negligible compared to protons and neutrons.

2. Atomic Number ($Z$):

   • Represents the number of protons in the nucleus of an atom.

   • Identifies an element. All atoms of a given element have the same atomic number.

3. Mass Number ($A$):

   • The sum of the number of protons and neutrons in an atom's nucleus.

   • $A = Z + ext{number of neutrons}$

4. Isotopes:

   • Atoms of the same element (same number of protons) that have different numbers of neutrons, and thus different mass numbers.

   • Example: Carbon-12 ($6$ protons, $6$ neutrons) and Carbon-14 ($6$ protons, $8$ neutrons).

2.2 The Periodic Table

1. Organization:

   • Elements are arranged by increasing atomic number.

   • Periods (Rows): Horizontal rows where elements have increasing atomic numbers.

   • Groups (Columns/Families): Vertical columns where elements have similar chemical properties.

2. Classification of Elements:

   • Metals: Typically solid, shiny, good conductors of heat and electricity, malleable, and ductile. Located on the left and center of the periodic table.

   • Nonmetals: Generally not shiny, poor conductors of heat and electricity. Can be solid, liquid, or gas at room temperature. Located on the right side of the periodic table.

   • Metalloids (Semimetals): Possess properties intermediate between metals and nonmetals. Found along the zigzag line separating metals and nonmetals.

3. Important Groups (Families):

   • Group 1A (1): Alkali Metals - Highly reactive metals (except hydrogen).

   • Group 2A (2): Alkaline Earth Metals - Reactive metals.

   • Group 7A (17): Halogens - Highly reactive nonmetals.

   • Group 8A (18): Noble Gases - Very unreactive gases.

4. Periodic Trends:

   • Atomic Size: Generally decreases across a period and increases down a group.

   • Ionization Energy: The energy required to remove an electron. Generally increases across a period and decreases down a group.

   • Electronegativity: