Atomic theory

Aristole

200

Aristole believed that matter could be broken down into four elements; earth, air, fire, and water. He also believed that their was no limit to the number of times that matter could be divided. People accepted his beliefs for centuries. Until More experiments were done later on.

John Dalton

Oct 30, 1803

Born on 1766. He believed tthat atoms are tiny, indestructible particles with no internal structure. "The main points of Dalton's theory are as follows; All are composed of atoms. All atoms of the same element have the same mass, and atoms of different elements have different masses. Compounds contain atoms of more than one element. In a particular compound, atoms of different elements always combine in the same way."

J.J Thomson

Oct 30, 1897

Believed that electrons are embedded in a sphere of of positive electric charge. Thomson's model was a chocolate chip ice cream model. The vanilla ice cream repesents the positively charged mass of matter. The chocolate chips are spread evenly throughout the ice cream which represents the negative charge. The negative charges balance out the positive charges in the vanilla ice cream.

Hantaro Nagaoka

Oct 31, 1904

A Japanese physicist. Born in 1865, suggested that atoms have a central nucleus. Also that the electrons move in orbits. Like the rings around Saturn.

Ernest Marsden

Nov 1, 1909

born in 1891. Did an experiment with Rutherford. He actually helped him with his theory. His experiment was with a sheet of gold and shot a beam of alpha particles at the sheet. This experiment helped Rutherford conclude that the positive charge of an atom is not evenly spread throughout thr atom.

Ernest RutherFord

Oct 31, 1911

Born in 1871. Staed that an atom's nucleus is dense with a positive charge. He also beleived that the electrons moved randomly around the nucleus. He tested his hypothesis with an experiment. With the help of Ernest Marsden he discovered that the positive charge of an atom is not evenly spread throughout the atom.

Niels Bohr

Oct 31, 1913

Was born in 1885. Bohr was a Danish physicist who worked with Rutherford. Mostly agreed with rutherford's theory but focused more on the electrons. He believed that the electrons orbited around the nucleus at fixed distances. Also beleived that if electrons lost or gained energy that they could change. This is called energy levels.

Henry Moseley

Nov 1, 1913

born in 1887. Was influenced by Rutherford. He actually created Moleley's Law. The law stated that all the positively charged electrons are located in the nucleus. Also associated with the atomic number.

Max Planck

Nov 1, 1913

Born in 1858. Was a German physicist. He created the Quantum Theory. This theory helps us better understand atomic and subatomic processes.

Lois de Broglie

Oct 31, 1924

Born in 1892. Believed that electrons had properties of waves in some conditions. He found that atoms did not act like a solar system because electrons did not move in regular orbits.

Erwin Schrodinger

Oct 31, 1926

Born in 1887. Developed equations to describe the motion of electrons and his work lead to the electron cloud model. His equation gave wave function which squared gave the probability of the cloud of electrons.

James Chadwick

Oct 31, 1932

Born in 1891. cofirmed the presence of neutrons. The neutrons have no charge. Also the atom nuclei contains nuetrons and posively charged protons.

Democritus

Mar 2, 2022

Was born in 460 B.C. With the help of Leucippus believed that everything is made of atoms and between atoms is empty space. Also that atoms are indestructible, indivisible, and are always in motion. Also believed that different types of atoms have different properties. Ex: Liquid atoms were smooth and round, while the atoms in solids were rough and prickly.