Evolution of chemistry

Ancient Greek, Indian, Mayan, and Chinese philosophies all considered air, water, earth and fire as primary elements.

In Europe, the study of chemistry was conducted by alchemists with the goals of transforming common metals into gold or silver and inventing a chemical elixir that would prolong life. Although these goals were never achieved, there were some important discoveries made in the attempt.
⦁ the royal society was founded in England

Robert Boyle
⦁ Robert Boyle defined element, acid and base.
Robert Boyle(1627-1691) studied the behavior of gases and discovered the inverse relationship between volume and pressure of a gas. He also stated that “all reality and change can be described in terms of elementary particles and their motion,” an early understanding of atomic theory. In 1661, he wrote the first chemistry textbook, “The Sceptical Cymist,” which moved the study of substances away from mystical associations with alchemy and toward scientific investigation.
⦁ The French academy of science was founded.


⦁ Georg Brandt discovered Cobalt in his Swedish laboratory.
[Miners in the Harz mountains have often been frustrated by a substance which appears to be copper ore but which, when heated, yields none of the expected metal. Even worse, it emits noxious fumes.]

⦁ Axel Cronstedt discovered Nickel in Sweden.
A similar demon is blamed by miners in Saxony for another ore which yields a brittle substance instead of copper. The impurity in ore of this type is analyzed in Sweden in 1751 by Axel Cronstedt. He identifies its components as arsenic and a previously unknown hard white metal, quite distinct from copper.

Joseph Black, the Scottish Chemist
⦁ Black explored the properties of a gas produced in various reactions. He found that ⦁ limestone could be heated or treated with acids to yield a gas he called "fixed air." He observed that the fixed air was denser than air and did not support either flame or animal life. Black also found that when bubbled through an aqueous solution of ⦁ lime (⦁ calcium hydroxide), it would precipitate calcium carbonate. He used this phenomenon to illustrate that ⦁ carbon dioxide is produced by animal ⦁ respiration and ⦁ microbial ⦁ fermentation.

Henry Cavendish
⦁ Henry Cavendish had set up a small laboratory in his house. He collected some iron, lead and tin pieces, besides hydrochloric acid. He then put an equal number of iron pieces in both acids. He did the same with the lead and tin piece producing hydrogen. As a result of the chemical process some bubbles surfaced. He collected the gas bubbles in separate balloons. He noticed that all the balloons contained samples of inflammable gases and they all produced similar blue flame. On further observation he found that the gases weighed the same and the volume of inflammable gas produced was proportionate to the metal pieces.

⦁ Joseph Priestley and discovery of Oxygen.
On August 1, 1774, he conducted his most famous experiment. Using a 12-inch-wide glass "burning lens," he focused sunlight on a lump of reddish mercuric oxide in an inverted glass container placed in a pool of mercury. The gas emitted, he found, was "five or six times as good as common air." In succeeding tests, it caused a flame to burn intensely and kept a mouse alive about four times as long as a similar quantity of air.
In October 1774, Priestley visiting Paris with his noble patron, he describes his discovery to a gathering of French scientists. Among them is Lavoisier, who develops Priestley's experiments in his own laboratory and realizes that he has the evidence to disprove the phlogiston theory. He named it oxygen [meaning acid maker].

Antoine Lavoisier, the French Chemist.

Lavoisier's Elementary Treatise of Chemistry, 1789, was the first modern chemical textbook, and presented a unified view of new theories of chemistry, contained a clear statement of the Law of Conservation of Mass, and denied the existence of phlogiston. In addition, it contained a list of elements, or substances that could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur. His list, however, also included light, and caloric, which he believed to be material substances.
Lavoisier made many fundamental contributions to the science of chemistry. Following Lavoisier's work, chemistry acquired a strict quantitative nature, allowing reliable predictions to be made. The revolution in chemistry which he brought about was a result of a conscious effort to fit all experiments into the framework of a single theory. He established the consistent use of chemical balance, used oxygen to overthrow the phlogiston theory, and developed a new system of chemical nomenclature.

In 1779 Lavoisier coined the name oxygen for the element released by mercury oxide. He found oxygen made up 20 percent of air and was vital for combustion and respiration. He also concluded that when phosphorus or sulfur are burned in air, the products are formed by the reaction of these elements with oxygen.

In 1777 Lavoisier correctly identified sulfur as an element. He had carried out extensive experiments involving this substance and observed that it could not be broken down into any simpler substances.
In 1778 Lavoisier found that when mercury oxide is heated its weight decreases. The oxygen gas it releases has exactly the same weight as the weight lost by the mercury oxide.
While this may seem obvious to us today, it was less so in those days (hence the general support for the phlogiston theory). After carrying out work with a number of different substances, and recalling earlier work such as his work in 1772 with carbon, Lavoisier announced a new fundamental law of nature:
The law of conservation of mass:
⦁ matter is conserved in chemical reactions
     or stated in another way:
⦁ the total mass of a chemical reaction’s products is identical to the total mass of  the starting materials
The law of mass conservation only became firmly established after Lavoisier independently discovered it.

In 1783 Lavoisier coined the name ‘hydrogen’ for the gas which Henry Cavendish had recognized as a new element in 1766; Cavendish had called the gas inflammable air.
Working again with Pierre-Simon Laplace, Lavoisier burned hydrogen with oxygen and found that water was produced, establishing that water is not an element, but is actually a compound made from the elements hydrogen and oxygen. This result astonished many people, because at that time ‘everyone knew’ that water was itself one of the ‘indivisible’ element
In1789 Lavoisier published his groundbreaking work “Elementary Treatise on Chemistry.” 
Elementary Treatise on Chemistry detailed his oxygen theory of chemistry (banishing phlostigon), made clear the difference between a compound and an element, and contained a list of chemical elements. The list included oxygen, nitrogen, hydrogen, sulfur, phosphorus, carbon, antimony, cobalt, copper, gold, iron, manganese, molybdenum, nickel, platinum, silver, tin, tungsten, and zinc.
Antoine Lavoisier is called, the father of modern chemistry.
In 1794, Joseph Proust studied pure chemical compounds and stated the Law of Definite Proportions — a chemical compound will always have its own characteristic ratio of elemental components. Water, for instance, always has a two-to-one ratio of hydrogen to oxygen.
Amedeo Avogadro (1776-1856) was an Italian lawyer who began to study science and mathematics in 1800. Expanding on the work of Boyle and Charles, he clarified the difference between atoms and molecules. He went on to state that equal volumes of gas at the same temperature and pressure have the same number of molecules. The number of molecules in a 1-gram molecular weight (1 mole) sample of a pure substance is called Avogadro’s Constant in his honor. It has been experimentally determined to be 6.023 x 1023 molecules and is an important conversion factor used to determine the mass of reactants and products in chemical reactions.
In 1803, an English meteorologist began to speculate on the phenomenon of water vapor. John Dalton (1766-1844) was aware that water vapor is part of the atmosphere, but experiments showed that water vapor would not form in certain other gases. He speculated that this had something to do with the number of particles present in those gases. Perhaps there was no room in those gases for particles of water vapor to penetrate. There were either more particles in the “heavier” gases or those particles were larger. Using his own data and the Law of Definite Proportions, he determined the relative masses of particles for six of the known elements: hydrogen (the lightest and assigned a mass of 1), oxygen, nitrogen, carbon, sulfur and phosphorous.
Dalton explained his findings by stating the principles of the first atomic theory of matter.

The main points of Dalton's atomic theory  are:

⦁ Elements are composed of extremely small particles called atoms.
⦁ Atoms of the same element are identical in size, mass and other properties. Atoms of different elements have different properties.
⦁ Atoms cannot be created, subdivided or destroyed.
⦁ Atoms of different elements combine in simple whole number ratios to form chemical compounds.
⦁ In chemical reactions atoms are combined, separated or rearranged to form new compounds.

Dmitri Mendeleev (1834-1907) was a Russian chemist known for developing the first Periodic Table of the Elements. He listed the 63 known elements and their properties on cards. When he arranged the elements in order of increasing atomic mass, he could group elements with similar properties. With a few exceptions, every seventh element had similar properties (The eighth chemical group — the Noble Gases — had not been discovered yet). Mendeleev realized that if he left spaces for the places where no known element fit into the pattern that it was even more exact. Using the blank spaces in his table, he was able to predict the properties of elements that had yet to be discovered. Mendeleev’s original table has been updated to include the 92 naturally occurring elements and 26 synthesized elements.
The term "element" is used for atoms with a given number of protons, as well as for a pure chemical substance consisting of a single element (e.g. hydrogen gas).
Dmitri Mendeleev published a periodic table of the chemical elements in 1869 based on properties that appeared with some regularity as he laid out the elements from lightest to heaviest.When Mendeleev proposed his periodic table, he noted gaps in the table and predicted that as-then-unknown elements existed with properties appropriate to fill those gaps. He named them eka-boron, eka-aluminium and eka-silicon, with respective atomic masses of 44, 68, and 72. For example, germanium was called eka-silicon until its discovery in 1886,
The four predicted elements lighter than the rare-earth elements, eka-boron, eka-aluminium, eka-manganese, and eka-silicon, proved to be good predictors of the properties of scandium, gallium, technetium, and germanium  respectively, which fill the spot in the periodic table assigned by Mendeleev.
Atomic Number as the Basis for the Periodic Law
Assuming there were errors in atomic masses, Mendeleev placed certain elements not in order of increasing atomic mass so that they could fit into the proper groups (similar elements have similar properties) of his periodic table. An example of this was with argon (atomic mass 39.9), which was put in front of potassium (atomic mass 39.1). Elements were placed into groups that expressed similar chemical behavior.
In 1913 Henry G.J. Moseley did researched the X-Ray spectra of the elements and suggested that the energies of electron orbitals depend on the nuclear charge and the nuclear charges of atoms in the target, which is also known as anode, dictate the frequencies of emitted X-Rays. Moseley was able to tie the X-Ray frequencies to numbers equal to the nuclear charges, therefore showing the placement of the elements in Mendeleev's periodic table.