Search results
Results From The WOW.Com Content Network
The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries.
6th - 2nd Century BCE Kanada (philosopher) proposes that anu is an indestructible particle of matter, an "atom"; anu is an abstraction and not observable. [1] 430 BCE [2] Democritus speculates about fundamental indivisible particles—calls them "atoms"
Joseph Priestley and Antoine Lavoisier discover a new gas called oxygen, discrediting the basic theory of chemistry at the time, creating the basis for the modern science of chemistry, and prompting chemists all over the world to look for more new elements; Humphry Davy introduces audiences to nitrous oxide ("laughing gas") and uses electricity to search for new chemical elements.
In this book Krauss discusses creating parts of an oxygen atom, the primary atoms of the Big Bang.Then he follows it through the remaining history of the Universe.As time has been passing by, the atom was a part of a supernova and star dust, star and planet systems, and, ultimately, a part of living cells.
Bohr Model of the Atom The Bohr model, proposed by Niels Bohr in 1913 , is a revolutionary theory describing the structure of the hydrogen atom. It introduced the idea of quantized orbits for electrons, combining classical and quantum physics.
In 1904, Thomson suggested a model of the atom, hypothesizing that it was a sphere of positive matter within which electrostatic forces determined the positioning of the corpuscles. [1] To explain the overall neutral charge of the atom, he proposed that the corpuscles were distributed in a uniform sea of positive charge.
Moreover, he proposed that an atom tended to form an ion by gaining or losing the number of electrons needed to complete a cube. Thus, Lewis structures show each atom in the structure of the molecule using its chemical symbol. Lines are drawn between atoms that are bonded to one another; occasionally, pairs of dots are used instead of lines.
If an atom has more electrons than protons, then it has an overall negative charge, and is called a negative ion (or anion). Conversely, if it has more protons than electrons, it has a positive charge, and is called a positive ion (or cation). The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force.