Periodic Law
The periodic table visually represents the periodic law, which states that the chemical and physical properties of
elements are dependent on their atomic numbers in a periodic manner.
Arrangement of Elements
The modern periodic table organizes elements into periods (horizontal rows) and groups or families (vertical
columns) based on atomic number. There are seven periods corresponding to the principal quantum numbers n = 1
through n = 7 for s- and p-block elements.
Sequential Filling of Periods
Each period is filled sequentially, meaning that each element in a given period has one additional proton and one
additional electron compared to the element immediately to its left when considering their neutral states.
Groups and Chemical Properties
Groups consist of elements that share the same electronic configuration in their valence shell, leading to similar
chemical properties among them. The electrons located in the valence shell, known as valence electrons, are
positioned farthest from the nucleus and possess the highest potential energy.
Higher Potential Energy and Chemical Bonds
Valence electrons possess higher potential energy and are held less tightly by the nucleus compared to inner
electrons. This characteristic enables them to participate in chemical bonding with the valence electrons of other
atoms. Consequently, the configuration of these valence shell electrons is crucial in determining an element’s
chemical reactivity and its properties.
Valence Electrons and Group Classification
The Roman numeral assigned to each group in the periodic table indicates the number of valence electrons present
in elements within that group when they are in their neutral state. These groups are further classified into two
categories:
1. Representative Elements (Group A): This category includes groups IA through VA, where elements have their
valence electrons located in the s or p orbitals.
2. Nonrepresentative Elements (Group B): This category encompasses transition elements, which have valence
electrons in both s and d subshells, as well as lanthanide and actinide series elements that have valence
electrons in s and f subshells.
Conclusion
Understanding the arrangement and behavior of valence electrons is essential for predicting how different elements
will react chemically, based on their position within the periodic table.
Electron Configuration of Representative Elements The electron configuration of representative elements is
determined by their Roman numeral and letter designation. For instance, elements in Group VA possess five valence
electrons with a configuration that includes the p orbital.