The nature of elements changes drastically with even a unit change in their atomic number due to the organization of electrons in atoms. The atomic number of an element is equal to the number of protons in the nucleus of its atom, which determines its unique identity.
The behavior and properties of an element are primarily determined by the arrangement and distribution of electrons in its atomic structure. Electrons occupy energy levels or shells around the nucleus, and each energy level can accommodate a certain maximum number of electrons. The innermost shell can hold a maximum of 2 electrons, while the subsequent shells can accommodate more.
Elements in the periodic table are arranged in order of increasing atomic number, and as the atomic number increases, so does the number of electrons. When the atomic number increases by just one unit, it means an additional proton and an additional electron are present in the atom. This extra electron occupies the next available energy level or shell.
The arrangement of electrons in these shells determines an element's chemical properties, such as its reactivity, ability to form compounds, and the nature of its chemical bonds. The outermost shell, known as the valence shell, is particularly important in determining an element's chemical behavior. The number of electrons in the valence shell influences how readily an element can gain, lose, or share electrons to form chemical bonds.
Therefore, when the atomic number changes by one unit, the addition or removal of an electron can significantly impact an element's chemical behavior and reactivity. Elements in the same group or column of the periodic table often exhibit similar chemical properties because they have the same number of valence electrons.
In summary, the nature of elements changes drastically with even a unit change in their atomic number because it directly affects the arrangement of electrons and their interaction with other atoms, leading to variations in chemical behavior and properties.