Atomic Size, Ionization Energy, & Electronegativity
1.c. – Students know how to use the periodic table to identify
alkali metals, alkaline earth metals and transition metals, trends in
ionization energy, electronegativity, and the relative sizes of ions
and atoms.
• Mendeleev understood the ‘Periodic Law’
which states:
• Atoms with similar properties appear in groups or
families (vertical columns) on the periodic table.
• They are similar because they all have the same
number of valence (outer shell) electrons, which
governs their chemical behavior.
• There are several other important atomic
characteristics that show predictable trends that
you should know.
1. Atomic size
2. Ionization Energy
3. Electronegativity
• Atoms at the bottom of the periodic table are
BIGGER than atoms at the top!
1
2
3
4
5
6
E7
E5
7
E3
E2
E1
nucleus
E4
E6
• As we go down a group each
atom has another energy
level…So the atoms get
bigger.
H
Li
Na
K
Rb
• Atoms on the left
side of the
periodic table are
bigger than
atoms on the
right side of the
periodic table.
• As we move across a period….protons are
added….this increases the nuclear charge (+)!
• As protons are added….electrons are also
added….so the electrostatic attraction increases
(positive & negative attraction)!
• This attraction pulls the outermost electrons in
Nato the nucleus….making
Mg
Al
Si thePatomSsmaller!
Cl Ar
closer
_
_
++
• Atomic size tends to increase from right to left
and from top to bottom.
• Ionization Energy - amount of energy needed
to remove an electron from an atom.
• It is harder to remove an electron from smaller
atoms because the nucleus is closer and better
able to hold on to them.
• It is easier to take electrons from larger atoms
because the electrons are further from the
nucleus.
• It is easier to take electrons from metals since
they want to LOSE electrons!
LOW
IONIZATION
ENERGY
Medium-High
IONIZATION
ENERGY
Very High
IONIZATION
ENERGY
• Ionization Energy tends to increase from left
to right and from bottom to top.
• Electronegativity - ability of an atom to attract
an electron.
• It is easier for small atoms to attract an
electron because the nucleus is closer and is
better able to hold on to them.
• It is easier for nonmetals to gain electrons.
• Electronegativity tends to increase from left
to right and from bottom to top.
Metals
Metalloids
(Semimetals)
Nonmetals
Left Side
Alkali
Alkaline Earth
Transition
Elements dividing the
metals and nonmetals
(stair-step line)
Right Side
Halogens
Noble Gases
Give up (Lose) eCations
Give up (Lose) eOr Accept (Gain) e-
Accept (Gain) e(Noble gases do not gain e-)
Anions
Big Atomic Size
Small Atomic Size
Low Ionization
High Ionization
Low Electronegativity
High Electronegativity
(Excluding Noble Gases)
Cornell Questions
• As you move across a Period, how does the
atomic number change?
• As you move across a Period, how does the
“pull” of the nucleus on the electrons change?
• As you move across a Period, how does the
atomic size, ionization energy, and
electronegativity change?
• As you move down a Group, how does the
atomic size, ionization energy, and
electronegativity change?
Create a Periodic Table Trends
Periodic Table
1. Number the rows and groups
2. Draw increasing arrows representing atomic
size (must be in color)
3. Draw increasing arrows representing
ionization energy (must be in a different
color)
4. Draw increasing arrows representing
electronegativity (must be in a different color)