Periodic Trends-1

Periodic Trends

• Key Trends:

  • Atomic Radius

  • Metallic Character

  • Ionization Energy

  • Electron Affinity

  • Electronegativity

Old Terms to Know

• Valence Electrons (Valence e-):

  • Outer electrons that are the most energetic.

• Atomic Number Trends:

  • Down a Family: Increases.

  • Across a Period: Increases.

Atomic Radius

• Definition:

  • The radius of an atom can be found by measuring the distance between the nuclei of two touching atoms and halving that distance.

  • Note: Disregard noble gases in the radius trend.

Coulombic Attraction

• Concept:

  • Many properties are related to the attraction of the positive nucleus for the negative electrons.

• Factors Influencing Attraction:

  • Quantity of charge.

  • Distance of charge.

Trends in Atomic Size

• Influenced by Two Factors:

  • Energy Level:

  • More energy levels equate to a larger atom.

  • Charge on Nucleus:

  • More charge pulls electrons in closer.

Group Trends

• As We Go Down a Group:

  • Each atom has another energy level, so the atoms get bigger.

  • Example Group: H, Li, Na, K, Rb.

Periodic Trends

• As You Go Across a Period:

  • The atomic radius gets smaller.

  • Same energy level.

  • More nuclear charge.

  • Outermost electrons are closer.

  • Example Period: Na, Mg, Al, Si, P, S, Cl, Ar.

Ionic Size

• Metal Cations:

  • Formed by losing electrons.

  • Cations are smaller than the atom they originate from.