The atomic and ionic radii, as we know, generally decrease in a period from left to right. As a consequence, the ionisation enthalpies generally increase (with some exceptions) and electron gain enthalpies become more negative across a period. In other words, the ionisation enthalpy of the extreme left element for a period is the least and the electron gain enthalpy of the element on the extreme right is the highest negative (Note: noble gases having completely filled shells have rather positive electron gain enthalpy values). This results in high chemical reactivity at the two extremes and the lowest in the centre.
Group - 1 elements form basic nature oxides. Metallic oxides are basic in nature because they react with dilute acids to form salt and water, while group - 17 elements form acidic oxides, An oxide that exhibits the property of acids is called acidic oxide. Since they are acidic, they react with a base to form a salt. Non-metals react with oxygen to form acidic compounds of oxides which are held together by covalent bonds. Therefore, statement - II is true.