G-tidings Success Hub

The periodic table.

The periodic table is a chart that organizes all known chemical elements by increasing atomic numbers, arranging them in rows (periods) and columns (groups) to show recurring chemical properties.
Elements are arranged from the lowest atomic number, hydrogen, to the element with the highest atomic number,

Key Features
Organization: Elements are ordered by atomic number (number of protons).

Periods (Rows): Horizontal rows where properties gradually change.

Groups (Columns): Vertical columns where elements share similar chemical behaviors (e.g., Group 1 are alkali metals).

Blocks: The table is divided into blocks (s, p, d, f) based on electron configurations, with the f-block usually placed below for space.

Blocks: Metals, nonmetals, and metalloids (semimetals) are separated by a diagonal line, with metals on the left and nonmetals on the upper right.

Image credit @ Google

Ideal Gas vs Real Gas
- *Ideal Gas:*
- Hypothetical gas that follows *ideal gas law (PV = nRT)* perfectly.
- Assumptions:
- Molecules have *zero volume*.
- No intermolecular forces.
- *Real gases ≈ ideal* at *high T + low P*.

- *Real Gas:*
- Actual gases that *deviate* from PV = nRT (esp. at high P, low T).
- *Factors causing deviation:*
- Molecules have *volume*.
- Intermolecular forces (attraction/repulsion).

Key Differences

Property Ideal Gas Real Gas
Volume of molecules Zero Non-zero
Intermolecular forces None. Present
Equation PV = nRT (e.g., Van der Waals)
Behavior Obeys gas laws. always Deviates (esp. near liquefaction)
Van der Waals Equation (for real gases)
*(P + an²/V²)(V - nb) = nRT*
- *a:* accounts for attraction between molecules.
- *b:* accounts for molecular volume

Examples & When Real Gases ≈ Ideal
- *Real gases ≈ ideal* at:
- *High temperature (T)* → molecules move fast, forces negligible.
- *Low pressure (P)* → molecules far apart, volume & forces ≈ zero.

Examples
1. *H₂, He, Ne (at normal T & P):*
- *≈ Ideal* → weak forces, small size.
2. *CO₂, NH₃ (at normal T & P):*
- *Not ideal* → stronger forces, liquefy easily.
3. *At high P (e.g., 100 atm):*
- Most gases ≠ ideal → volume & forces matter.

When Real → Ideal
- *↑ T, ↓ P* → ideal behavior.
- *H₂ at 25°C, 1 atm* → ≈ ideal.
- *Steam (H₂O gas) at 100°C, 1 atm* → ≠ ideal (strong H-bonds).