Examples of atom in the following topics:
-
- Atoms contain negatively charged electrons and positively charged protons; the number of each determines the atom's net charge.
- The number of protons in an atom defines the identity of the element (an atom with 1 proton is hydrogen, for example, and an atom with two protons is helium).
- However, because electrons can be transferred from one atom to another, it is possible for atoms to become charged.
- Atoms in such a state are known as ions.
- If a neutral atom gains an electron, it becomes negative.
-
- Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model.
- In this model the atom was also sometimes described to have a "cloud" of positive charge.
- With this model, Thomson abandoned his earlier "nebular atom" hypothesis, in which the atom was composed of immaterial vortices.
- Now, at least part of the atom was to be composed of Thomson's particulate negative corpuscles, although the rest of the positively charged part of the atom remained somewhat nebulous and ill-defined.
- His conclusions led him to propose the Rutherford model of the atom.
-
- Philosophical proposals regarding atoms have been suggested since the years of the ancient Greeks, but John Dalton was the first to propose a scientific theory of atoms.
- For this reason, Dalton is considered the originator of modern atomic theory.
- Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
- Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
- Atoms can be broken down into smaller pieces, and atoms of a given element can vary in mass and other properties (see isotopes and ions).
-
- Atoms with more than one electron are referred to as multielectron atoms.
- Atoms with more than one electron, such as Helium (He) and Nitrogen (N), are referred to as multielectron atoms.
- Hydrogen is the only atom in the periodic table that has one electron in the orbitals under ground state.
- The shielding theory also explains why valence shell electrons are more easily removed from the atom.
- For example, consider a sodium cation, a fluorine anion, and a neutral neon atom.
-
- In 1913, after returning to Copenhagen, he began publishing his theory of the simplest atom, hydrogen, based on the planetary model of the atom.
- One big puzzle that the planetary-model of atom had was the following.
- This atom model is disastrous, because it predicts that all atoms are unstable.
- Therefore, his atomic model is called a semiclassical model.
- Niels Bohr, Danish physicist, used the planetary model of the atom to explain the atomic spectrum and size of the hydrogen atom.
-
- Atom is a basic unit of matter that consists of a nucleus surrounded by negatively charged electron cloud, commonly called atomic orbitals.
- The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons.
- The electrons of an atom are bound to the nucleus by the electromagnetic (Coulomb) force.
- Hydrogen-1 (one proton + one electron) is the simplest form of atoms, and not surprisingly, our quantum mechanical understanding of atoms evolved with the understanding of this species.
- Thereafter, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed.
-
- The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.
- The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.
- As an example, the electron configuration of the neon atom is 1s2 2s2 2p6 or [He]2s2 2p6 , as diagramed in .
- The molecular orbitals are labelled according to their symmetry, rather than the atomic orbital labels used for atoms and monoatomic ions: hence, the electron configuration of the diatomic oxygen molecule, O2, is 1σg2 1σu2 2σg2 2σu2 1πu4 3σg2 1πg2.
- In the Aufbau Principle, as electrons are added to atoms, they are added to the lowest orbitals first.
-
- In alpha decay an atomic nucleus emits an alpha particle and transforms into an atom with smaller mass (by four) and atomic number (by two).
- As the result of this process, the parent atom transforms ("decays") into a new atom with a mass number smaller by four and an atomic number smaller by two.
- Because an alpha particle is the same as a helium-4 nucleus, which has mass number 4 and atomic number 2, this can also be written as:
- This convention is not meant to imply that the nuclei necessarily occur in neutral atoms.
- An atomic nucleus emits an alpha particle and thereby transforms ("decays") into an atom with a mass number smaller by four and an atomic number smaller by two.
-
- The electrons of an atom are bound to the nucleus by the electromagnetic force.
- Democritus called this the atom.
- The Greeks also felt that atoms were in constant motion, another correct notion.
- He also believed that atoms are the indivisible, ultimate particles of matter.
- Describe postulates of Dalton's atomic theory and the atomic theories of ancient Greek philosophers
-
- The Rutherford model is a model of the atom named after Ernest Rutherford.
- Thomson's so-called "plum pudding model" of the atom was incorrect.
- Rutherford's new model for the atom, based on the experimental results, contained the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom.
- This central volume also contained the bulk of the atom's mass .
- This was in a gold atom known to be about $10^{-10}$ meters in radius; a very surprising finding, as it implied a strong central charge less than $\frac{1}{3000}$th of the diameter of the atom.