Georgina L, Christina M and Ilenia D

→ Democritus hypothesized that atoms cannot be split no matter what their size and this statement supported his other hypothesis which stated that atoms are indestructible, indivisible and always in motion. → Democritus titled his new discovery ‘atomos’, which is known today as the ‘atom’. → The scientist gave complex explanations on how planets, stars and systems of the Universe formed and after developing his atomic theory, Democritus was identified as the founder of modern Science. → Democritus’s mentor ‘Leucippus’, originally came up with the atomic theory which was later adopted by Democritus. → According to Democritus atoms were miniscule quantities of matter. Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible. → He believed that there are an infinite number of atoms. This hypothesis was created in 450BC approximately. → His atomic theory stated that “The universe is composed of two elements: the atoms and the void in which they exist and move.” Georgina L

Democritus’ atomic theory summarised: ‍1. All matter consists of invisible particles called atoms. ‍2. Atoms are indestructible. ‍3. Atoms are solid but invisible. ‍4. Atoms are similar. ‍5. Atoms differ in size, shape, mass, position, and arrangement.  Solids are made of small, pointy atoms.  ‍Liquids are made of large, round atoms.  ‍Oils are made of very fine, small atoms that can easily slip past each other. Democritus’ atomic model: Democritus’ atomic model: Democritus’ atomic model assisted scientists in further developing their understanding of the universe and what it’s made of by supplying a basic model for the atom. Democritus’ model consisted of a plain sphere containing no sub particles, such as protons, neutrons and electrons. The model does not display a nucleus, but helped in the development of the atomic theory by supplying a basic insight on the construction of the atom. Georgina L

Isaac Newton, born on the 25 th of December 1642 in Woolsthorpe, England, proposed that the universe consisted of small solid masses in motion. Newton, who became a maths professor at the ripe age of 26,suggested that atoms were held together by attractions that can be known as universal forces. The scientist died in 1727 Isaac Newton provided the basic classical mechanics and mathematics which were vital to the further development of the atomic theory initially proposed by Democritus. Scientists later used Newton’s theories and hypothesis’ to develop their theories, thus allowing for the development of the atomic theory. Georgina L

“Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy (1808).” -Wikipedia John Dalton, born in September 1766 in Cumberland, England, proposed a vital set of laws which correlate with atoms and the way they function. These set of laws stated that: 1)Elements are made of extremely small particles called atoms. 2)Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. 3)Atoms cannot be subdivided, created, or destroyed. 4)Atoms of different elements combine in simple whole- number ratios to form chemical compounds. 5)In chemical reactions, atoms are combined, separated, or rearranged. 6)And most importantly, Atoms and Elements are different. Aside from being burdened with colour blindness, Dalton constructed an atomic model which described that atoms were tiny, indivisible, indestructible particles and that each one had a certain mass, size, and chemical behaviour. John Dalton was inspired by Democritus’s initial attempts at developing an atomic theory, and ergo, built his ideas upon historical discoveries made by Democritus. Georgina L

Dmitri Mendeleev, a Russian scientist born in Tobolsk, Siberia in 1834, deciphered a way to clearly sort the 63 known elements into an understandable, simple table now known as the ‘Periodic’ table. In 1869, Mendeleev, after delving into the difficulties of sorting and organising the 63 elements, experienced a dream which would alter his way of thinking and lead him to create the periodic table. The Russian scientist organised the atoms according to their atomic mass due to being unaware of their structures. Mendeleev purposely left spaces in the periodic table for the remaining missing elements which were yet to be discovered or whose mass was unknown. However, he also predicted the existence and properties of new elements. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties. Mendeleev studied science at St. Petersburg and graduated in 1856 and, after his death in 1907, is best known for constructing the timeless table used by millions today. Georgina L

Joseph John Thomson ( )  Thomson was a British physicist and Nobel laureate.  He suggest that the fundamental unit was over 1000 times smaller than an atom.  In 1904 Thomson proposed the plum pudding model where electrons were embedded in the atom.  In 1906 He discovered that hydrogen had only a single electron for atom.  In 1912 He discovered that neon had two types of isotopes, that have two different atomic masses.

Ernest Rutherford ( )  was a New Zealand-born British chemist and physicist  who became known as the father of nuclear physics.  In 1899 He coined the terms alpha ray and beta ray to describe the two types of radiation  He showed that the atom consisted of a positively charged nucleus and negatively charged called electrons

Nielsen Bhor ( 1885–1962)  The electrons can only travel in certain orbits (called by Bohr as the "stationary orbits"): at a certain discrete set of distance from the nucleus.  The electrons of an atom revolve around the nucleus in orbits. These orbits are associated with definite energies.  The electrons jump from one shell to another.

Albert Einstein (1879 –1955)  In 1907 Einstein proposed a model of matter where each atom in a lattice structure is an independent harmonic oscillator.

Erwin Schrodinger Erwin Schrodinger was born on August 12, 1887 in Vienna. Schrodinger began to think about explaining the movement of an electron in an atom as a wave. By 1926 he published his work providing a theoretical basis for the atomic that Niels Bohr had proposed based on laboratory evidence. It became known as Schrodinger’s wave equation. This was the second theoretical explanation of electrons in atom, following Werner Heisenberg’s matrix mechanics. Schrodinger showed that the two theories were identical, only expressed differently. He won the Nobel Prize with Paul Dirac. Schrodinger continued to work with quantum physics until his death in 1961.

James Chadwick James Chadwick was born on the 20 th October, 1891 in Cheshire, England. In 1932, Chadwick discovered that the particle in the nucleus of the atom that became known as the neutron because it has no electrical charge. In contrast with the helium nuclei which are charged, this new tool is capable penetrating and splitting the nuclei of even the heaviest elements. This discovery prepared the way towards the fission of uranium and towards the creation of the atomic bomb. For this discovery he was awarded Hughes Medal of the Royal Society in 1932 and the Nobel Prize for Physics in Chadwick died in Cambridge on July 24, 1974.

Enrico Fermi Enrico Fermi was born on the 29 th September, 1901 in Rome, Italy. He is most known for his work on beta decay, the development of the first nuclear reactor and for the development of the quantum theory. After James Chadwick’s discovery scientists worked to discover more about the interior of the atom. In 1934, Fermi came up with an idea to use neutrons as projectiles instead of helium nuclei. He would shoot a neutron like arrow into an atoms nucleus. Many of the nuclei absorbed the extra neutron creating isotopes for every element. This was not the only discovery that he made. He found out that slowing down a neutron would make it have a larger impact on the nucleus. Later on in Fermi’s life he discovered the nuclear chain reaction. This led to the construction of atomic bombs and nuclear power. For these discoveries Fermi won many awards. Fermi passed away on November 29, 1954 to stomach cancer.

Higgs Boson The Higgs Boson is a very recent discovery as it was only discovered on the 4 th July, A new boson has been discovered and it behaves like the Standard Model Higgs. The discovery of this boson would be proof of an invisible energy field that fills the vacuum of space. It is still likely to take a few more years of research to find out whether the new particle is a simple Higgs boson or if it’s part of something more complex.

Georgina L