Modern Periodic Table Overview

The Modern Periodic Table

• Consists of 7 periods (horizontal rows) and 18 groups (vertical columns).
• Organized by atomic number, atomic mass, and electron configuration.
• Contains 118 elements classified by their physical state.

Elements by Physical State

• Solid elements: Most elements are solids.
  • Examples: Lithium (Li), Sodium (Na), Carbon (C), Phosphorus (P), Iron (Fe).
• Liquid elements: Two elements are liquid at room temperature.
  • Mercury (Hg): The only liquid metal.
  • Bromine (Br): The only liquid nonmetal.
• Gaseous elements: Eleven elements are gases at room temperature.
  • Nonmetals: Hydrogen (H), Nitrogen (N), Oxygen (O), Fluorine (F), Chlorine (Cl).
  • Inert gases: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn).

Arrangement of Elements

• Mendeleev's Periodic Table: Arranged by atomic mass.
• Moseley's Periodic Table: Arranged by atomic number.
• Modern Periodic Table: Arranged by atomic number and electron configuration.

Comparison of Groups

• Group 1A (Alkali Metals): Metals with 1 valence electron. Example: Lithium (Li).
• Group 2A (Alkaline Earth Metals): Metals with 2 valence electrons. Example: Beryllium (Be).
• Group 7A (Halogens): Nonmetals with 7 valence electrons. Example: Fluorine (F).
• Group 0 (Noble Gases): Inert gases with 8 valence electrons (except helium, which has 2). Example: Neon (Ne).

d-Block Elements

• Located in the middle of the periodic table, separating s-block and p-block elements.
• All are metals.
• Classified as transition metals and begin appearing in period 4.

f-Block Elements

• Located at the bottom of the periodic table.
• All are metals.

p-Block Elements

• Located on the right side of the periodic table.
• Contains all nonmetals with electron configurations ending in 5, 6, or 7 electrons.
• Includes all noble gases and some metals.
• Includes all metalloids.

Metalloids

• Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te).
• Exhibit properties of both metals and nonmetals.

Lewis Dot Structure

• A method to represent valence (outermost shell) electrons using dots around an element's symbol.
• Valence electrons are represented by dots distributed individually first and then paired until all are accounted for.
• The number of unpaired (single) electrons in the Lewis structure indicates the valency of the element.

Main Blocks of the Periodic Table

• s-Block: Consists of groups 1A and 2A, located on the left side of the periodic table.
• p-Block: Consists of six groups labeled with the letter A (excluding group 0), located on the right side of the periodic table.
• d-Block: Located in the middle of the periodic table, contains transition metals.
• f-Block: Located at the bottom of the periodic table, contains rare earth elements.

Moseley's Contribution

• Discovered that atomic numbers are more important than atomic masses for classifying elements.
• Rearranged Mendeleev's table by atomic number.
• Added inert gases and other elements to the table.

Moseley's Key Modifications to Mendeleev's Table

• Arranged elements in ascending order by atomic number.
• Added the group of inert gases to the table.
• Added other elements discovered after Mendeleev’s table was designed.

Modern Periodic Table

• Based on atomic numbers and electron configuration.
• More accurate and consistent than Mendeleev's table.

Electron Configuration and the Periodic Table

• Elements of the same group: Have similar number of electrons in their outermost energy level.
• Elements of the same period: Have similar number of filled energy levels.

Electron Configuration Observations

• Most metals have electron configurations ending in 1, 2, or 3 electrons.
• Most nonmetals have electron configurations ending in 5, 6, or 7 electrons.
• Noble gases have electron configurations ending in 8 electrons (except helium).