How to calculate valency of atoms?​

Explanation:

Mathematically we can say that if the outermost shell of an atom contains 4 or less than 4 electrons, then the valency of an element is equal to the number of electrons present in the outermost shell and if it is greater than 4, then the valency of an element is determined by subtracting the total number of electrons ...

The valency of a molecule is zero.

Explanation:

Valency is calculated by calculating number of electrons present in outermost orbitals of atom of element.

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definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.