Answer:
Hydrogen and helium are placed in different groups in the periodic table because they have different atomic numbers and different chemical properties......................................
Step-by-step explanation:
In the periodic table, the elements are arranged according to their atomic number, which is the number of protons in the nucleus of an atom. The elements are also organized into groups, or families, based on their chemical properties.
Hydrogen and helium are placed in different groups in the periodic table because they have different atomic numbers and different chemical properties. Hydrogen is placed in group 1a, also known as the alkali metals, because it has a single valence electron, which is an electron that is involved in chemical bonding. Helium, on the other hand, is placed in group 8a, also known as the noble gases, because it has a full valence shell, which means that it does not readily form chemical bonds.
It is important to note that the arrangement of elements in the periodic table is not based on the choices or preferences of the elements themselves, but rather on their intrinsic properties, such as their atomic number and chemical behavior.