Mendeleev’s periodic table is an arrangement of elements in an increasing atomic mass order in a tablet form, such that it reflects similarities and trends in the behaviour of elements. Mendeleev’s periodic table can be understood better by reversing the arrangement of the elements.
- Here elements are, arranged in an increasing order atomic mass, in a horizontal line.
- This horizontal arrangement of elements is a ‘period’.
- When an element has high similarity to an earlier element, the new element is, placed just below the earlier element having similar properties to start a new period.
- The period’s one below the other form a ‘column’ (group). Thus, Mendeleev’s periodic table consists of horizontal rows and vertical columns or periods and groups, respectively.
- If the element is similar but not very much, it is, placed below but slightly away to differentiate it. Each column will have two sub-columns (A and B) such that elements in the same sub-columns show more resemblance.
(a) Eka-Silicon was replaced by germanium, Eka-aluminium was replaced by Gallium
- Germanium (Ge) – Group 14, Period 4
- Gallium(Ga) – Group 13, Period 4
(c) Germanium is a metalloid and Gallium is a metal.
(d) Germanium(Ge) has 4 electrons, Gallium(Ga) has 3 valence electrons.