Dmitry Mendeleyev 

The Russian chemist Dmitry Mendeleyev is regarded as the father of the periodic table of chemical elements.

He studied all the elements known at the time and discovered that they showed a regular repetition of properties when arranged in a certain order. He also predicted the discovery and properties of new elements. All of these have now been isolated and named; one, mendelevium, is named for Mendeleyev. Mendeleyev also experimented with agricultural production based on scientific principles, increasing its efficiency to such an extent that his methods came to be applied in many Russian industries.

Antoine Lavoisier 

The French chemist Antoine Lavoisier is regarded as the father of modern chemistry. He is remembered particularly for his work on gases, gunpowder, and combustion. He discovered and named both oxygen and hydrogen, observing that these two gases combine to produce water. This led him to describe elements and compounds, giving many the names by which they are known today. Lavoisier and his wife Marie (1758–1836) were meticulous scientists who produced some important manuals describing scientific experiments. In the aftermath of the French Revolution, Lavoisier was executed by revolutionaries.