Periodic Table and Periodicity Notes

The periodic table organizes elements by their properties into groups (columns) and periods (rows). Key information for each element includes:

• Symbol: One or two-letter abbreviation.

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

• Relative Atomic Mass: Average mass relative to carbon-12.

• Standard State: Physical state at standard conditions (25 °C, 101 kPa).

Element Categories:

• Metals: Good conductors, malleable, ductile.

• Nonmetals: Poor conductors, brittle.

• Metalloids: Semi-conductors with mixed properties.

• Alkali Metals (Group 1): Highly reactive, forming +1 ions.

• Alkaline Earth Metals (Group 2): Reactive, forming +2 ions.

• Transition Metals: D-block metals with variable oxidation states.

• Chalcogens (Group 16): Includes oxygen, oxidation states of -2, +6, +4.

• Halogens (Group 17): Reactive nonmetals, form -1 ions.

• Noble Gases (Group 18): Inert gases.

• Lanthanides and Actinides: Inner transition metals.

Historical Insights:

• Dmitri Mendeleev: Organized elements by atomic weight, predicted gaps for undiscovered elements.

• Henry Moseley: Arranged by atomic number, leading to the modern periodic table.

Periodic Trends:

• Atomic Radius: Decreases across a period, increases down a group.

• Ionization Energy: Increases across a period, decreases down a group.

• Electronegativity: Increases across a period, decreases down a group.

• Electron Affinity: Varies based on atomic structure.