-
Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through space until stopped. Differences in atomic shape. Society determined the various properties of matter -
Theorizes that these solid forms of matter are composed of indivisible elements shaped like triangles (contrary to the popular conception of atoms as spheres). He believes triangles must be the correct form because they can join to make very different kinds of shapes. -
Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through space until they stopped—differences in atomic shape. Society determined the various properties of matter.
-
According to the alchemists, metals were created from two elements - mercury and sulfur. Mercury gave metals their fluidity and malleability, while sulfur accounted for their combustibility and contributed to their body and calcination (rusting). -
According to the alchemists, metals were created from two elements - mercury and sulfur. Mercury gave metals their fluidity and malleability, while sulfur accounted for their combustibility and contributed to their body and calcination (rusting).
-
In his early atomic theory known as atomism, he believed that everything was made up of tiny particles. He referred to these particles as corpuscles. To understand the nature and behavior of these corpuscles, he conducted numerous chemical experiments. -
- In his early atomic theory known as atomism, he believed that everything was made up of tiny particles. He referred to these particles as corpuscles. To understand the nature and behavior of these corpuscles, he conducted numerous chemical experiments.
-
Antoine Lavoisier's book "Elementary Treatise of Chemistry" was published in 1789, where he defined elements as chemicals that cannot be broken down into other substances through chemical analysis. He also introduced the atomic theory model, which was based on the law of conservation of mass, and explained how matter was conserved during chemical changes. -
Antoine Lavoisier's book "Elementary Treatise of Chemistry" was published in 1789, where he defined elements as chemicals that cannot be broken down into other substances through chemical analysis. He also introduced the atomic theory model, which was based on the law of conservation of mass, and explained how matter was conserved during chemical changes.
-
The billiard ball model defined an atom as a ball-like structure because atomic nucleus and electrons were unknown at the time. -
As per the theory, matter consists of tiny, indivisible particles known as atoms. The theory further states that all atoms of a specific element have identical properties and masses. The last part of the theory suggests that compounds are created by combining two or more different types of atoms. -
As per the theory, matter consists of tiny, indivisible particles known as atoms. The theory further states that all atoms of a specific element have identical properties and masses. The last part of the theory suggests that compounds are created by combining two or more different types of atoms.
-
In 1811, the Italian chemist Amadeo Avogadro (1776-1856) proposed a principle stating that gases of equal volume at the same temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties. This number is known as Avogadro's number, which is 6.023 X 10²³. -
His newly formulated law was announced before the Russian Chemical Society in March 1869 with the statement “Elements arranged according to the value of their atomic weights present a clear periodicity of properties.” Mendeleev's law allowed him to build up a systematic table of all the 70 elements then known. -
Millikan’s work demonstrated that electrons did have a discrete, quantifiable charge. Thomson had also already calculated the charge-to-mass ratio of an electron, so once Millikan was able to measure the elementary charge, the mass of an electron could also be calculated. -
Millikan’s work demonstrated that electrons did have a discrete, quantifiable charge. Thomson had also already calculated the charge-to-mass ratio of an electron, so once Millikan was able to measure the elementary charge, the mass of an electron could also be calculated.
-
J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively charged electrons embedded within a positively charged "soup." -
In 1898 French physicists Pierre and Marie Curie discovered the strongly radioactive elements polonium and radium, which occur naturally in uranium minerals. Marie coined the term radioactivity for the spontaneous emission of ionizing, penetrating rays by certain atoms. -
The pudding model of the atom used the analogy of electrons being like plums embedded inside a uniform sphere of positive charge like blueberries stuck into a muffin. This analogy was significant in helping to explain the distribution of electric charges within the atom and was a major step toward our understanding of atomic structure. -
- Einstein also in 1905 mathematically proved the existence of atoms, and thus helped revolutionize all the sciences using statistics and probability. The atomic theory says that any liquid is made up of molecules (invisible in 1905). Furthermore, these molecules are always in random, ceaseless motion.
-
Einstein also in 1905 mathematically proved the existence of atoms in, and thus helped revolutionize all the sciences using statistics and probability. The atomic theory says that any liquid is made up of molecules (invisible in 1905). Furthermore, these molecules are always in random, ceaseless motion.
-
In 1911, Rutherford described the atom as having a tiny, dense, and positively charged core called the nucleus. Rutherford established that the mass of the atom is concentrated in its nucleus. The light, negatively charged, electrons circulated this nucleus, much like planets revolving around the Sun. -
Henry Moseley collected the x-ray spectra of a variety of elements and found that the frequency of x-ray radiation has a precise mathematical relationship to an element's atomic number. This relationship is now called Moseley's Law and allowed scientists a new, more accurate way to organize elements. -
In 1913, scientist Niels Bohr proposed a groundbreaking theory for the hydrogen atom. Based on quantum theory, the theory suggested that certain physical quantities can only take on discrete values. According to Bohr's model, electrons move around the nucleus in specific orbits, and if an electron transitions to a lower-energy orbit, the energy difference is emitted as radiation. -
In 1913, scientist Niels Bohr proposed a groundbreaking theory for the hydrogen atom. Based on quantum theory, the theory suggested that certain physical quantities can only take on discrete values. According to Bohr's model, electrons move around the nucleus in specific orbits, and if an electron transitions to a lower-energy orbit, the energy difference is emitted as radiation.
-
The Bohr model describes atoms as having a nucleus with electrons orbiting around it, similar to the solar system. It's a simplified representation that helps scientists understand basic atomic properties, despite its limitations -
Erwin Schrödinger's theory explained the behavior of electrons within atoms by treating them mathematically as matter waves, based on de Broglie's idea that particles exhibit wavelike behavior. -
The Electron Cloud is a region surrounding an atom's nucleus where electrons move randomly. Its size and shape depend on electron energy level and number in the outermost shell. Despite its elusive nature, it's essential in understanding atoms and their interactions. This was made by Erwin Schrödinger -
James Chadwick is known for his discovery of the neutron in the atom and its contribution to Atomic Theory. While experimenting with the other scientists, Chadwick discovered a subatomic particle with no electric charge.