Transcript Chapter 8

Chapter 8
Relationships
in the
Periodic Table
A Brief Overview
A
The Periodic Table
Of
The Elements
Atomic Number Increases
Ionization Energy Increases
Atomic Number Increases
Ionization Energy Decreases
Metallic Properties Increase
Atomic Radius Increases
Metallic Properties Decrease
Atomic Radius Decreases
A Series of Properties:
Atomic Radius - one half the distance between the two
nuclei in a covalent homonuclear molecules.
Metals
Diatomic Molecules
Atomic Radius increases from top to bottom and
decreases from left to right in the table.
Ionic Radius:
•Corresponds to an ion
•Cationic Radius - smaller than atomic due to
decrease in repulsive and increase in attractive
forces
•Anionic Radius - larger than atomic due to
increase in repulsive forces
Ca
Loses 2
electrons
Ca+2
Ionization Energy
The minimum energy required to remove an electron
from a gaseous atom in its ground state.
energy +X(g) ----> X+ (g) + eenergy + X+----> X+2(g) + e- second ionization
energy + X+2 ----> X+3 (g) + e- third ionization
I1 < I2 < I3 <…
Increases from bottom to top and from left to right in the
Periodic Table.
Electron Affinity:
The energy exchange associated with an element when
it accepts electrons in a molecular environment.
Electronegativity:
The tendency of an element in an isolated gaseous
state to attract an electron toward itself.
Electronegativity increases from bottom to top and
left to right in the periodic table.
As you move from left to right in the periodic table you are
putting electrons on the same shelf, so the shielding stays
constant. At the same time you are increasing the positive
charge in the center. This is the cause of many of the trends we
have observed:
A
The Periodic Table
Of
The Elements
Atomic Number Increases
Ionization Energy Increases
Atomic Number Increases
Ionization Energy Decreases
Metallic Properties Increase
Atomic Radius Increases
Metallic Properties Decrease
Atomic Radius Decreases
Summary of Facts and Concepts:
1.Nineteenth century chemists developed the periodic
table by arranging elements in the increasing order of
their atomic masses. Discrepancies in early versions of
the periodic table were resolved by arranging the
elements in order of their atomic numbers.
2.Electron configuration determines the properties of an
element. The modern periodic table classifies the
elements according to their atomic numbers, and thus
also by their electron configurations. The configuration
of the valence electrons directly affects the properties of
the atoms of the representative elements.
3. Periodic variation in the physical properties of the
elements reflect differences in atomic structure. The
metallic character of elements decreases across a period
from metals through the metalloids and increases from top
to bottom within a particular group of representative
elements.
4. Atomic radius varies periodically with the arrangement
of the elements in the periodic table. It decreases from
left to right and increases from top to bottom.
.Ionization energy is a measure of the tendency of an atom
to resist the loss of an electron. The higher the ionization
energy, the stronger the attraction between the nucleus
and an electron. Electron affinity is a measure of the
tendency of an atom to gain an electron.
The more positive the electron affinity, the greater the
tendency for the atom to gain an electron. Metals
usually have low ionization energies, and non-metals
usually have high electron affinities.
5. Noble gases are very stable because their outer ns
and np subshells are completely filled. The metals
among the representative elements (in Groups 1A,2A,
and 3A) tend to lose electrons until their cations become
isoelectronic with the noble gases that precede them in
the periodic table. The nonmetals in Groups 5A,6A,
and 7A tend to accept electrons until their anions
become isoelectronic with the noble gases that follow
them in the periodic table.
Key Words:
Amphoteric Oxide
Atomic Radius
Diagonal Relationship
Electron Affinity
Ionic Radius
Ionization Energy
Isoelectronic
Noble Gases
Representative Elements
Valence Electrons