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118 / 118 Elements

S Solid L Liquid G Gas

← Swipe horizontally to explore full 18-column table →

Rare Earth Elements (f-block Series):

Lanthanides

Actinides

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Periodic Table Guide

1. Periods vs. Groups

Periods (Horizontal Rows): Elements in the same period share the same principal quantum energy shell for their outermost electrons. As you move left-to-right across a period, atomic radius decreases while electronegativity generally increases.

Groups (Vertical Columns): Elements in the same vertical group share the same number of valence electrons, resulting in closely matched chemical reactivity and bonding characteristics.

2. The Quantum Blocks (s, p, d, f)

s-block: Groups 1 & 2 + Helium (Spherical orbital, holds 2e⁻)

p-block: Groups 13 through 18 (Dumbbell orbitals, holds 6e⁻)

d-block: Groups 3 through 12 (Transition metals, holds 10e⁻)

f-block: Lanthanides & Actinides (Rare earths, holds 14e⁻)

3. Major Periodic Trends

Electronegativity: Increases toward the top-right (Fluorine is the highest at 3.98). Noble gases typically have negligible values.
Atomic Radius: Increases toward the bottom-left (Francium has the largest atomic radius).
Ionization Energy: The energy required to remove the most loosely held electron; peaks at the top-right (Helium is the highest).

4. Bohr Electron Shell Rules

According to Bohr-Stoner quantum rules, each principal energy level n holds a maximum of 2n² electrons:

K (n=1): 2

L (n=2): 8

M (n=3): 18

N (n=4): 32

5. Natural States at STP

At standard temperature & pressure (298.15 K, 1 atm):
• Only 2 elements are liquid: Bromine (Br) and Mercury (Hg).
• 11 elements are gases: Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, and all 6 noble gases.
• The remaining elements are solids under terrestrial room conditions.