Time Line of Matter

Events

Stone Age Chemists

8000 B.C - 6000 B.C

Once these first chemist learned how to control fire, they learned how to change many substances to their advantage, for example, they could fire-harden bricks to strengthen them and cook their food. Eventually, the ability to control fire led to the production of glass and ceramic material.

Early Interest in Metals and Liquid Matter

6000 B.C. - 1000 B.C.

Early chemists only investigated on high-value materials to humans, such as gold and copper. gold was very valuable because of its properties such as color, luster and that it didn't tarnish. Copper was also valuable because it could be used to make pots, coins, tools, and jewelry. Untreated copper is brittle and weak. However, when copper is heated it can be rolled into sheets or stretched into long wires. Later experimenting with copper let to the creation of a strong hard material known as bronze, which is made when copper and tin are melted and mixed together.

Beginning of Iron Age

1200 B.C.

A group of people called the Hittites discovered how to extract iron from rocks and turn it into a useful material. Eventually, people learned to combine iron with carbon to produce an even harder material called steel, steel meant they could make stranger blades and stronger armour.

Early ideas About the Composition of Matter

500 B.C.

The idea that all matter is made up of particles started with Greek philosophers. They observed that a rock could be smashed into smaller and smaller pieces until it became a powder, but they wondered, how much they could continue to break down the powder until it couldn't be broken down anymore? In 400 B.C. the Greek philosopher Democritus used the word atomos to describe the smallest particles that could not be broken down further. Atomos means "invisible". Democritus stated that each type of material was made up of a different type of atomos. He believed these different particles gave each material its own unique set of properties. In 350 B.C. another Greek philosopher, Aristotle, supported a different believed in something else. He suggested that everything was made of earth, air, fire, and water.

Alchemy to Chemistry

499 B.C. - 1500

for the next 2000 years after Democritus' time, experiments with matter were mainly done by alchemists, people who were part magician, and part scientist. Alchemist believed it should be possible to turn lead into gold. Even though they weren't real scientists, alchemist performed some of the first chemistry experiments. In doing so, they invented many useful tools that we still use today.

Invention of Plaster of Paris and the First Chemistry Text Ever

1501 - 1600

The Arab alchemist al-Razi discovered what we now know as plaster of Paris, a material that today's doctors still use to hold broken bones in place until they heal. In 1597 the German alchemist Andreas Libau published Alchemia, a book describing the achievements of alchemists. He also explained how to prepare chemicals such a hydrochloric acid. this type of information made his book the first chemistry text ever.

New Interest in Atoms

1601 - 1769

From the late 1500s on, people started to investigate more into the world around them. They had a greater interest in understanding the nature of matter change that alchemists had. In the 1660s, Robert Boyle experimented with the behavior of gases and other substances. Through his experiments and observations, Boyle was sure that matter was made up of tiny particles, just as Democritus had said in about 400 B.C. Boyle felt that the purpose of chemistry was to determine the types of particles making up each substance.

Chemistry Develops as a New Science

1780 - 1807

in the 1770s a French scientist by the name of Antoine Laurent Lavoisier studied chemical reactions. by the late 1780s, he had developed a system for naming chemicals, this was significant, for now, all scientists could use the same words to describe their observations. This made it much easier to compare the results of their experiments. Because of this, Lavoisier is called the "father of modern chemistry."

An Atomic Theory Takes Shape

1808 - 1897

in 1808 English scientist John Dalton used the observations from his experiments to develop his own theory of the composition of matter. Dalton said that matter was made up of elements. Dalton also put forward the first modern theory of atomic structure. He stated that each element was composed of a particle called an atom. All atoms of a particular element, he said are identical in mass, and no two elements have atoms of the same mass. Daltons model is sometimes called the "billiard ball model" because he thought of the tiny atoms as solid spheres.

Adding Electrons To The Atomic Model

1809 - 1904

Daltons work on the structure of the atom was continued by British physicist J.J. Thompson. He is credited with being the first person to discover a subatomic particle. Thompson experimenting with cathode rays he concluded that the rays were made up of streams of negatively charged particles. He showed these particles were much smaller than a hydrogen atom. He named them electrons. In 1897 Thompson proposed what was called the "raisin bun model" of the atom. He described the atom as a positively charged sphere in which negatively charged electron were embedded in it like raisins embedded in a bun. The negative electrons balance the positive sphere so the whole atom has no electrical charge. In 1904, the Japanese physicist Hantaro Nagaoka refined the model of the atom further. The model resembles a miniature solar system. At the center of the atom was a large positive charge. The negatively charged electrons orbited around like planets orbiting around a star.

A Canadian Contribution To Atomic Theory

1905 - 1907

Support for the Nagaoka model and the idea of a central nucleus came from the British scientist Ernest Rutherford. Using Thompsons model, Rutherford conducted experiments in which he shot positively charged particles through thin gold foil. He predicted that all the high-speed particles would pass straight through the foil without being affected by the gold atoms. Instead, the results showed that while most particles did behave as he predicted, some were greatly deflected. to explain why this might of happened, Rutherford proposed a new model. He suggested that atoms were mainly empty space through which the positive particles could pass, but at the core was a tiny positively charged center. This he called the nucleus.

Bohr's Model

1922 - Present Day

It was Niels Bohr who, working with Rutherford, suggested that electrons do not randomly orbit in an atom. Bohr said that they move in specific circular orbits, or electron shells. He believed electron jumped between these shells by gaining or losing energy. Bohr's model was readily accepted, though with further refinements by James Chadwick, another British physicist. Chadwick discovered that the nucleus contained positively charged particles called protons and neutral particles called neutrons. Today, most people still use Bohr's model to describe the particles that make up the atom.