Periodicity Regular periodic variations table

Regular periodic variations of properties of elements with atomic number (and position in the periodic table). 

Representative Elements. The A group elements in the periodic table are called representative elements. Their last electron is assigned to an outer shell s or p orbital. These elements show distinct and fairly regular variations in their properties with changes in atomic number. 

Lesson 1 Lesson 2 Lesson 3 -Introduction to the Periodic Table. -Variations in atomic and ionic radii across Period 3. -Variations in melting points and electrical conductivities across Period 3 Regular instruction - expository, questioning and group discussion. 

The periodic law is an organized "map" of the elements that relates their structure to their chemical and physical properties. It states that the elements, when arranged according to their atomic numbers, show a distinct periodicity (regular variation) of their properties. The periodic table is the result of the periodic law. 

It is observed that the number of hydrogen atoms with which an individual atom of various elements will combine varies cyclically from one side of the periodic table to another. This demonstrates periodicity—regular variations in the behavior of the elements. 

It should be noted that there is not always this consistency in property variations withm the periodic table. Physical properties change in a more or less regular manner however, there are some rather abrupt changes when one moves across a period or down a group. 

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