Learning Target
1. I will be able to explain electronegativity
and relate it to the trend on the periodic table.
2. I will be able to identify the most
reactive metallic element in the periodic table
3. I will be able to identify the most
reactive nonmetallic element in the periodic table
Atomic Radii
The atomic radius of a chemical element
is a measure of the size of its atoms, usually
the mean or typical distance from the nucleus
to the boundary of
the surrounding cloud of electrons.
Ion
• An ion is an atom or a molecule in which the
total number of electrons is not equal to the
total number of protons, giving the atom or
molecule a net positive or negative electrical
charge. Ions can be created, by either
chemical or physical means, via ionization.
Ionic Radii
• Ionic radius is the radius of an atom's ion.
Electronegativity
The ability of an
atom in a molecule
to attract shared
electrons to itself.
Linus Pauling
1901 - 1994
Electronegativities
1A
1
Period
2
3
4
5
6
7
8A
H
2.1
2A
3A
4A
5A
6A
7A
Li
Be
B
C
N
O
F
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Al
Si
P
S
Cl
1.5
1.8
2.1
2.5
3.0
Na Mg
0.9
1.2
3B
4B
5B
6B
7B
8B
K
Ca
Sc
Ti
V
Cr Mn Fe
Co
0.8
1.0
1.3
1.5
1.6
1.6
Rb
Sr
Y
Zr
0.8
1.0
1.2
Cs
Ba
La *
0.7
0.9
1.1
Fr
Ra
Ac
0.7
0.9
1.1
y
1B
2B
Ni
Cu
Zn
Ga
Ge
As
Se
Br
1.5
1.8
1.8
1.8
1.9
1.7
1.6
1.8
2.0
2.4
2.8
Nb Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
1.4
1.6
1.8
1.9
2.2
2.2
2.2
1.9
1.7
1.7
1.8
1.9
2.1
2.5
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
1.3
1.5
1.7
1.9
2.2
2.2
2.2
2.4
1.9
1.8
1.8
1.9
2.0
2.2
* Lanthanides: 1.1 - 1.3
yActinides:
1.3 - 1.5
Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 373
Below 1.0
2.0 - 2.4
1.0 - 1.4
2.5 - 2.9
1.5 - 1.9
3.0 - 4.0
Trend
As you go down the group, reactivity of the
metals increases, Atomic radii increases,
ionization energy decreases, electronegativity
Decreases, shielding increases.
It is easier to lose the valence electrons
and react forming compounds
Summary of Periodic Trends
Nuclear charge increases
Shielding increases
Atomic radius increases
Ionic size increases
Ionization energy decreases
Electronegativity decreases
Shielding is constant
Atomic radius decreases
Ionization energy increases
Electronegativity increases
Nuclear charge increases
1A
0
2A
Ionic size (cations)
decreases
3A 4A 5A 6A 7A
Ionic size (anions)
decreases