Why does the first ionization enthalpy increase as we go from to across a given period of the Periodic Table?

A quantitative measure of the tendency of an element to lose electron is given by its ionisation enthalpy (I.E.). I.E. increases from left to right in a period of the periodic table. However, in second period, the I.E of oxygen is less than that of nitrogen. Why?

The reactivity of an element is very much related to its ionization enthalpy. In general, ionization enthalpy increases from left to right across a period. Give the reason.

Explain the general periodic trend of first ionization enthalpy along a period and group in the periodic table.

Why does magnesium has a higher ionization enthalpy than sodium?

Ionization enthalpy is an important periodic property. a) What is the unit in which it is expressed? b) What are the factors influencing ionization enthalpy? c) How ionisation enthalpy varies in the periodic table?

a) Which is the element among alkali metals having lowest ionization enthalpy? b) What is meant by valence of an element? How it varies in the periodic table?

Atomic sizes generally increase as we come down a group of the periodic table. But in the 4th group of the periodic table, Zr and Hf have almost the same atomic sizes. Why?

Why has the zero group been placed at the extreme of the periodic table?

Name the elements included in the first period of the periodic table.

The electronegativity of elements from left to right in a period of periodic table.