Download Periodic Table Trends

Periodic Table Trends
Atomic Radius
• As you move down a group, atomic radius
increases
• The number of energy levels increases as you
move down a group as the number of
electrons increases. Each subsequent energy
level is further from the nucleus than the last.
Therefore, the atomic radius increases as the
group and energy levels increase
Atomic Radius
• As you move across a period, atomic radius
decreases
• As you go across a period, electrons are added to
the same energy level. At the same time, protons
are being added to the nucleus. The
concentration of more protons in the nucleus
creates a "higher effective nuclear charge." In
other words, there is a stronger force of
attraction pulling the electrons closer to the
nucleus resulting in a smaller atomic radius.
Atomic Radius
First Ionization Energy
• The energy required to remove the outermost (highest
energy) electron from a neutral atom in its ground
state
• As you move down a group, first ionization energy
decreases
• Electrons are further from the nucleus and thus easier
to remove the outermost one.
"SHIELDING" - Inner electrons at lower energy levels
essentially block the protons' force of attraction toward
the nucleus. It therefore becomes easier to remove the
outer electron
First Ionization Energy
• As you move across a period, first ionization
energy increases
• As you move across a period, the atomic
radius decreases, that is, the atom is smaller.
The outer electrons are closer to the nucleus
and more strongly attracted to the center.
Therefore, it becomes more difficult to
remove the outermost electron
First Ionization Energy
Electron Affinity
• The electron affinity of an atom or molecule is
defined as the amount of energy released
when an electron is added to a neutral atom
or molecule to form a negative ion.
• As you move down a group, electron affinity
decreases
• This is caused by the increase in atomic radius
Electron Affinity
• As you move across a period, electron affinity
increases
• This is caused by the decrease in atomic radius
Electron Affinity
Electronegativity
• Electronegativity measures an atom's strength
to attract and form bonds with electrons
• As you move to the right across a period of
elements, electronegativity increases
• When the valence shell of an atom is less than
half full it is easier to lose an electron.
Conversely, when the valence shell is more
than half full, it is easier to pull an electron
into the valence shell than to donate one.
Electronegativity
• As you move down a group, electronegativity
decreases
• The atomic number increases down a group
and thus there is an increased distance
between the valence electrons and nucleus, or
a greater atomic radius
Electronegativity