PERIODIC TABLE

Periodic Properties




Jerome Garcia

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.
 

Periodic Table

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.
 

Density

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.
 

Ionization Energy


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.
 

Electron Affinities

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.

Lesson Page

History of Periodic page

Related Links
 


http://rpsec.usca.sc.edu/Classwork/731sp2001/Lesson/Garcia/garcia3.html  (January, 2001)
"The views expressed are not necessarily those of the University of South Carolina."