SpED Notes by: Syed Zaidi
DATE CLASS TEACHER PERIOD HW
ATTACH.
ASSIGNMENT
12/13 Chem
Zizmor
E
Title: Periodic Trend
Alkaline Earth Metals reactivity increases as you go down the metal
family on periodic table.
Periodic Trends:
1. Reactivity
 Elements in the same family (column) tend to have the
same reactivity…
 This happens because they have the same valence
electron configuration
Halogen Reactivity Trends
 Halogens are all diatomic
 They come in a set of twins (they are really stuck together)
 As you go down the periodic table, the Halogens become less
reactive.
 Alkali metals react to lose electrons
 So, they get less reactive as you go down the column…more on
this later
2. Atomic Radius
 Size: atoms are very tiny (10^-12 = 1pm), but they are not
all the same size
 Going across the periodic table, atoms get smaller. There
are more protons, pulling electrons closer to them
 Going down the periodic table, atoms get larger. There are
more shells of electrons at greater distances from the
nucleus.
 Atomic Radius is biggest at the lower left hand side of the
periodic table and smallest at the upper right hand side of
the periodic table
Vocabulary
 Electron Shielding: Filled shells of electrons mask some of the
nuclear pull from the valence electron
 Effective Nuclear Charge: The pull of the nucleus that is felt by
the valence electrons through the electron shielding provided by
the core electrons. (Usually equal to the # of valence e-s)
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Shielding and ENC
As we go down the periodic table, Filled shells increases,
shielding increases, ENC increases BUT not enough…
Therefore…Atomic radius increases ability to loose e-s increases
and reactivity increases.
As we go across the periodic table, number of core electrons is
constant, electron shielding is constant, number of protons
increases therefore ENC increases.
AND
Electrons are held more tightly, so Atomic radius decreases,
making it easier to attract e-s.
3. Ionization energy:
 a measure of how much energy is needed to remove an
electron
 Li is talking to F (on periodic table) and it says “I’m going to
give you my valence electron, but it is going to cost you.
 As we go across they periodic table, effective nuclear
charge increases, electrons are held more tightly, atoms are
less willing to give them up, Ionization energy increases.
 As you go down the periodic table, the size increases,
electron shielding increases, effective nuclear charge can’t
keep up, atoms are more willing to give up e-s, Ionization
energy decreases.
 Ionization is the weakest at the lower left corner of the
periodic table and strongest at the upper right corner.
4. Electronegativity
 A measure of how much an atom can attract electrons on a
scale of 0 – 4.0
 0 – take this electron away from me!
 2 – I’ll take your electron, if you don’t want it.
 4 – I NEED an electron, give me your electron PLEASE!!
 Going down on the periodic table, atoms get bigger, electron
shielding gets bigger, effective nuclear charge cant keep up the
ability to attract, an electron goes down, Electronegativity goes
down.
 Going across periodic table, effective nuclear charge goes up,
atomic size goes down, electron shielding stays the same, the
atom is more attractive to electrons which leads to a high
electronegativity
 On a periodic table Fr has the smallest electronegativity to F
having the highest electronegativity
 Noble gasses do not have anything.