Question
What is the basic difference in approach between the Mendeleev's Periodic Law and the Modern Periodic Law?

Answer

Mendeleev's periodic law is based on atomic mass of elements while modern periodic table is based on atomic number. According to Mendeleev, "properties of elements are periodic functions of their atomic masses." While according to modern periodic law, "the physical and chemical properties of elements are periodic functions of their atomic numbers."

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Similar questions

Use the following thermodynamic data to calculate the enthalpy change for the formation of solid lithium fluoride, LiF(s) from Li(s) and F2(g):

$\text{Li(s)}+\frac{1}{2}\text{F}_2(\text{g})\overrightarrow{\ \ \ \ \ \ \ }\ \text{LiF(s)}$

$\text{Li(s)}\overrightarrow{\ \ \ \ \ \ \ \ }\ \text{Li(g)};$ $\Delta_\text{s}\text{H}^\circ=155\text{kJ mol}^{-1}$

$\frac{1}{2}\text{F}_2(\text{g})\overrightarrow{\ \ \ \ \ \ \ }\ \text{F(g)};$ $\Delta\text{H}^\circ=75\text{kJ}$

$\text{Li(g)}\overrightarrow{\ \ \ \ \ } \ \text{Li}^{+}(\text{g})+\text{e}^-;$ $\Delta\text{H}^\circ=520\text{kJ mol}^{-1}$

$\text{F(g)}+\text{e}^-\overrightarrow{\ \ \ \ \ \ } \ \text{F}^-(\text{g});$ $\Delta\text{H}^\circ=-333\text{kJ mol}^{-1}$

$\text{Li}^+\text{(g)}+\text{F}^-(\text{g})\overrightarrow{\ \ \ \ \ \ \ \ }\ \text{LiF(s)};$ $\Delta\text{H}^\circ=-1012\text{kJ mol}^{-1}$

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