PERIODIC TABLE OF ELEMENTS

PERIODIC TABLE OF ELEMENTS

1. Elements are arranged from left to right and top to bottom in order of increasing atomic number.

2. The rows are called periods.

3. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state)

4. The number of electrons in a period increases as one moves down the periodic table; therefore, as the energy level of the atom increases, the number of energy sub-levels per energy level increases.

5. Elements that occupy the same column on the periodic table (called a "group") have identical valance electron configurations and consequently behave in a similar fashion chemically.

6. 'Father' of the periodic table

   • Dmitri Mendeleev
     • He began ordering them by increasing atomic weight.
     • Arranged the elements according to both atomic weight and valence.

7. Reading the table

   • Atomic number
     • The number of protons in an atom is referred to as the atomic number of that element.
     • The number of protons defines what element it is and also determines the chemical behavior of the element.
   • Atomic symbol
     • Is an abbreviation chosen to represent an element
   • Atomic weight
     • The standard atomic weight of an element is the average mass of the element in atomic mass units (amu).
     • The atomic mass on the periodic table is stated as a decimal number because it is an average of the various isotopes of an element.

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