What makes the atomic radius change down a column of the periodic table

Explanation:

When we move down a group then there is increase in the size of elements because there occurs increase in atomic mass of the elements.

It means that there occurs increase in number of electrons due to which there will be increase in number of new shells. As a result, size of atom or element increases due to which there is increase in atomic radius of the element.

Therefore, we can conclude that increase in number of electrons makes the atomic radius change down a column of the periodic table.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.