Periodic Trends & Atomic Structure

Atoms follow predictable patterns across the periodic table based on their structure. These patterns, called periodic trends, help us understand why certain elements behave similarly while others are dramatically different.

Key periodic trends include atomic radius (size of atoms), ionization energy (energy needed to remove an electron), electron affinity (energy released when adding an electron), and electronegativity (ability to attract shared electrons). Atoms get smaller as you move across a period because the increasing number of protons (effective nuclear charge) pulls electrons more tightly.

The arrangement of electrons follows specific rules: the Aufbau Principle (electrons fill lowest energy orbitals first), Hund's Rule (orbitals are singly occupied before pairing), and the Pauli Exclusion Principle (no two electrons can have identical quantum numbers).

💡 Remember This: Trends follow predictable patterns - atomic size decreases across periods and increases down groups, while ionization energy and electronegativity do exactly the opposite!

Coulomb's Law $F=K(q₁q₂/r²)$ explains many of these trends by describing how charged particles attract or repel each other. Meanwhile, electromagnetic radiation (light) travels as waves with properties of wavelength (λ) and frequency (ν) that are inversely proportional $c=λν$. The energy of light can be calculated using Planck's equation: E=hν, where h is Planck's constant (6.626×10⁻³⁴ J·s).