Periodic Table §

• combines like elements together
  • like = similar electron configurations in Atoms
• columns are groups
• rows are periods
• organizes elements into families
  • similar chemical properties
  • arranged with increasing atomic number (z)
  • different ways to categorize
    • metals, nonmentals, metalloids
    • transition metals, main group, noble gases
    • alkali, alkaline-earth, chalcogens, halogens, lanthanides, actinides
• tells us how electrons are arranged for each element
  • as atomic number goes up, so does number of electrons
• trends are based on [[Electrons in Atoms#Quantum Numbers#Electron Configurations|similar electron configurations]]

Periodic Trends §

Size (Radial) §

• impacts reactivity, physical properties
• $\propto$ electron energy
• includes electrons
  • electron cloud is $10^5$ times larger than nucleus
• INCREASES WHEN
  • GOING DOWN
    • increases in principle quantum number
  • GOING LEFT
    • going right adds electrons to same valence
    • effective nuclear charge remains same going to the right
      • $Z_{\text{eff}}=Z-S$
        • $Z$ increases because increase in protons
        • $S$ (screening constant) because only adding core electrons increases screening

Ionization Energy §

• INCREASES WHEN
  • going UP
  • going RIGHT

Electron Affinity §

• INCREASES WHEN
  • going UP
    • less
  • going RIGHT

    • elements like Li and K can become noble gas if giving away electron

Electronegativity §

• INCREASES WHEN
  • going UP
  • going RIGHT