Trends & the Periodic Table

Trends Periodic Trends – patterns that can be seen with our current arrangement of the elements (Moseley) Trends we’ll be looking at: Atomic Radius Ionization Energy 3. Electronegativity

Atomic Radius Atomic radius: the radius of the atom. This is an indication of the atom’s volume. Affected by 1. # of energy levels 2. Proton Pulling Power

Increasing Atomic Radius

Group Trend                                                                                                                                                                                                                    Atoms at the bottom of the PT have more energy levels and subatomic particles which make the atomic radius bigger.

Period Trend As you go from left to right, you gain more protons (the atomic number increases) The more protons you have, the more Proton Pulling Power Because the nucleus are + and the electrons are – ,the electrons get pulled towards the nucleus.

More protons = greater PPP “proton pulling power” Period Trend More protons = greater PPP “proton pulling power”

Atomic Radius

Ionization Energy = amount energy required to remove a valence electron. Closely related to electronegativity.

Increasing Ionization Energy

Group Trend Elements at the bottom of PT have valence e- that are much further away from nucleus Inner electrons shield the charge felt by the valance e- (Shielding Affect) attraction much weaker so it’s easier to steal e- away

Period Trend Elements at the right of the PT are so close to achieving the “octet rule” This requires a lot of energy to take one of their e-

Electronegativity An atom’s “desire” to grab another atom’s electrons. noble gases tend not to form bonds, so don’t have electronegativity values

Increasing Electronegativity

Group Trend Elements near the top of the periodic table have few electrons; every electron is a big deal. They have a stronger desire to acquire more electrons. Elements near the bottom of the chart have so many electrons that loosing or gaining an electron is not as big a deal.

Period Trend Elements at the right of the PT are so close to achieving the “octet rule” They have a strong “desire” to achieve the octet. Elements on the left would rather give electrons away to drop down an energy level.

How do you know if an atom gains or loses electrons? Atoms form ions to get a valence of 8 (or 2 for H) Metals tend to have 1, 2, or 3 valence electrons It’s easier to lose them (CATIONS) Nonmetals tend to have 5, 6, or 7 valence electrons It’s easier to add some (ANIONS) Noble gases already have 8 so they don’t form ions very easily

Most reactive metal = Fr (the most metallic) Increased Electronegativity Increased Ionization Energy Increasing Atomic Radius Most Reactive Nonmetal = F Increased Electronegativity Increased Ionization Energy (easier to remove an electron) Increasing Atomic Radius Most reactive metal = Fr (the most metallic)