periodicity

atomic radius trends

• increase going from TOP to BOTTOM and RIGHT to LEFT

• more shielding, less protons (Zeff) to “tighten” the radius.

ionic radius trends

• within the same period, anions are always larger than cations.

• increase from TOP to BOTTOM (more shielding) and from RIGHT to LEFT (protons)

what is the trend for the isoelectronic series?

• as a positive nuclear charge INCREASES, the ionic radius DECREASES.

  • greater positive charge pull electrons closer to the nucleus.

• as negative charge DECREASES, the ionic radius INCREASES.

  • more negative ions experience electron repulsion, increasing radius.

ionization energy trend (energy required to remove an electron)

• increases going from LEFT to RIGHT and from BOTTOM to TOP.

electron affinity trend (energy of gaining an electron)

• increases from BOTTOM to TOP (less shielding) and LEFT to RIGHT (closer to the octet)

• more exothermic = more energy being released when an electron is added.

electronegativity trends (the ability of an atom to attract shared electrons in a covalent bond)

• increases from BOTTOM to TOP (less shielding) and LEFT to RIGHT (higher Zeff/more protons)

what are the reactivity trends for Group 1 alkali metals?

• high reactivity (increases going DOWN)

  • this trend can be explained with ionization: lower ionization (less attraction & stability) = easier electron loss = losing single electron = forms a positive ion = more reactivity in water.

what are the reactivity trends for group 17 halogens?

• high reactivity going UP 

  • as you go down, there is more shielding, so if you remove a valence electron, there isn’t much of a reaction since there’s less electrostatic attraction.