A graduate of University of South Florida with B.A. in chemistry. and
curently teaching at Glenn Hills High School. Mr. Garcia teaches
Physical Science and Chemistry.
Elements in the same column have similar outer level electron configurations
and the configurations change in a regular way from one column to the next
as we scan across the table. Because the properties of the elements
are determined by their electron configuration. When we scan the
periodic table from left to right, we should be able to periodic properties
of most elements based on our knowledge of the behavior of a few.
Properties are periodic. similar properties occur at certain intervals
of atomic number, as is stated in the modern periodic law.
Metals exist as solids at room temperture and have the highest desity while
nonmetals exist as gases at room temperature and at one atmosphere.
When the densities of the elements, are plotted against the atomic
numbers of the elements. The metals show to have a higher density
than the nonmetals Mercurry is the only metal that exist as a liquid
at room temperature while Bromine is the only nonmetal that is a liquid
at room temperature and one atmosphere.
Radii of the atoms
As you look at the periodic table from top to bottom, each period represents
a new, higher energy level (principal quantum number). As the principal
quantum number increases, the size of the electron cloud increases.
The size of atoms in each group increases as you look down the group.
Chemists discuss the size ot atoms by referring to their radii. When
you look across the periodic table, all the atoms in a period have the
same principal quantum number. This fact might leads you to expect
that all atoms in a period are similar size, but the positive charge on
the nucleus increases by one proton for each element in a period.
As a result, the outer cloud is pulled in a little tighter. Consequently,
one periodic property of atoms is that they generally decrease slightly
in size from left to right across a period of the table. In summary,
atomic radii increase top to bottom and right to left in the periodic table.
The energy required to remove an electron from an atom is call its
ionization energy. The energy required to remove the most loosely
held electron (first electron) is the first ionization energy. The
first ionization energy tends to increase as atomic number increases in
any horizontal row or period. In any column or group, there is gradual
decrease in first ionization energy as atomic number increases. In
general elements can be classified as metals or nonmetals on the basis
of first ionization energy. A metals are characterized by their low
first ionization energy and are located at the left side of the table.
An element with a high first ionization energy is a nonmetal and are located
to the right of the periodic table. The first ionization energies
decrease as you go down a column of the periodic table. The energy
decreases because of increased distance and the shielding effect.
The distance increases between the nucleus and the outer electrons and
the shielding effect in which inner electrons block the attraction of the
nucleus for the outer electrons, tends to lower the ionization energy.
The attraction of an atom for an electron is called electron affinity.
The same factors that afftect ionization energy also affect electron affinity.
In general, as electron affinity increases, an increase in ionization energy
can also be expected. Metals have low electron affinities and
nonmetals have high electron affinities. The general trend as we go down
the column is a decreasing tendency to gain electrons. For a nonmetal
the greater the electron affinity the greater the reactivity.
History of Periodic page
"The views expressed are not necessarily those of the University of