Transcript Periodic Trends - Duplin County Schools

Periodic Trends
Chemical Periodicity

Atoms participate in chemical reactions
in order to fill their outermost s and p
sublevels.
Some definitions…

ionization energy – energy required to
remove an electron from an atom

electron affinity – energy required to
add an electron to an atom

electronegativity – tendency of atoms
to attract e- when they are bonded to
another atom
Four Classes of Elements
Noble Gases
 outermost s, p filled
 do not react
Representative Elements
 outermost s or p only partially filled
Transition Metals
 outermost s filled
 adding e- to d sublevel
Inner Transition Metals
 outermost s sublevel is filled
 adding e- to f sublevel
Trends in Atomic Size
Within Groups:
 size increases as you move down
 e- are being added to additional energy
levels
Within Periods:
 size decreases left to right because of
increase in effective nuclear charge
 larger # of p+ causes atom to “shrink”
 inner e- shield nucleus
Effective Nuclear Charge
Trends in Atomic Size
Trends in Ion Sizes
cation
 positive ion
 atom LOSES electron(s)
 smaller than atoms from which they are
made
anion
 negative ion
 atom GAINS electron(s)
 larger than atoms from which they are
made
Relative Sizes of Cations
Relative Sizes of Anions
Trends in Ionization Energy
Within Groups:
 IE decreases as you move down
• e- are farther from nucleus
• e- not held as tightly in larger atoms
Within Periods:
 IE increases from left to right
 nucleus has greater attraction for e- in
smaller atoms
Ionization Energy
Trends in Ionization Energy
Trends in Electronegativity
Within Groups:
 decreases as you move down
 atoms too large for nucleus to attract eWithin Periods:
 increases left to right
 atoms get smaller, easier to attract e-
Trends in Electronegativity