EVERYDAY SCIENCE

Detailed explanation-1: -In the Periodic Table, with increase in atomic number, the metallic character of the elements. decreases in a period and increases in a group.

Detailed explanation-2: -In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present).

Detailed explanation-3: -As we go across a period from left to right, we add a proton to the nucleus and an electron to the valence shell with each successive element. As we go down the elements in a group, the number of electrons in the valence shell remains constant, but the principal quantum number increases by one each time.

Detailed explanation-4: -The correct order of the elements in the increasing order of their atomic numbers is given below: Helium (Z= 2) < Lithium (Z= 3) < Nitrogen (Z= 7) < Fluorine (Z= 9) < Magnesium (Z= 12).

Detailed explanation-5: -In 1913, English physicist Henry Moseley used X-rays to measure the wavelengths of elements and correlated these measurements to their atomic numbers. He then rearranged the elements in the periodic table on the basis of atomic numbers. This helped explain disparities in earlier versions that had used atomic masses.