Periodic Trend Notes
c4 Honors
re: 9/11 JG
Periodic Trends Notes from 9/21
WHAT IS A PERIODIC TREND?
-a predictable change that repeats
ex: seasons, months, days of the week, school day
ATOMIC RADIUS: one-half of the distance from the nucleus of two like
atoms.
TREND ACROSS a period (left to right): DECREASES
EXPLANATION: electrons enter the SAME energy level, as protons and
electrons are added the force between the protons and electrons
increase.The electrons are pulled closer to the nucleus making the atom
smaller.
TREND DOWN a family: INCREASES
EXPLANATION: as electrons are added to more energy levels,the inner
layers shield the outer electrons from the pull of the nucleus. The added
electrons have less attraction to the nucleus due to this shielding
effect, increasing the atom’s size
IONIZATION ENERGY: the amount of energy needed to remove an
electron from a specific atom
TREND ACROSS a period(left to right): INCREASES
EXPLANATION: the atom’s radius decreases, the electrons are held tighter
by the nucleus, so it will take more energy to remove an electron.
TREND DOWN a family: DECREASES
EXPLANATION: the atom’s radius increases, the electrons are held less
tightly by the nucleus, so it will take less energy to remove an electron.
Electronegativity: the attraction of an atom for an additional electron.
TREND ACROSS a period(left to right): INCREASES
EXPLANATION: the atom’s radius decreases,the nucleus has a stronger pull
on an extra electron
TREND DOWN a family: DECREASES
EXPLANATION: the atom’s radius increases, the nucleus has a weaker hold
onan extra electron
Ionic Radius:
positive ions become smaller and negative ions become bigger than their neutral
atom.
Other Notes:
valence electrons: number of electrons in the outermost energy level
isoelectronic: same number of electrons
These were not the only notes given in class you
must check with a friend the make other additions
to these basic notes!