atom

Examples of atom in the following topics:

• Tha New Atom

• Sample Atom

• Converting between Moles and Atoms

  • $x \ moles \cdot \frac {6.022\times10^{23} atoms}{1 \ mole} = y \ atoms$
  • $6 \ moles \cdot \frac {6.022\times 10^{23} atoms}{1 \ mole} = 3.61\times 10^{24} atoms$
  • $\frac{x \ atoms}{6.022\times 10^{23} \frac{atoms}{1 \ mole}} = y \ moles$
  • $x \ atoms \cdot \frac{1 \ mole}{6.022\times 10^{23} \ atoms} = y \ moles$
  • $3.5 \times 10^{24} \ atoms \cdot \frac{1 \ mole}{6.022\times 10^{23} \ atoms} = 5.81 \ moles$

• Hydrogen Bonding

  • A hydrogen bond is the electromagnetic attraction created between a partially positively charged hydrogen atom attached to a highly electronegative atom and another nearby electronegative atom.
  • A hydrogen atom attached to a relatively electronegative atom is a hydrogen bond donor.
  • In the molecule ethanol, there is one hydrogen atom bonded to an oxygen atom, which is very electronegative.
  • This hydrogen atom is a hydrogen bond donor.
  • Ethanol contains a hydrogen atom that is a hydrogen bond donor because it is bonded to an electronegative oxygen atom, which is very electronegative, so the hydrogen atom is slightly positive.

• Average Atomic Mass

  • The atomic number of an element defines the element's identity and signifies the number of protons in the nucleus of one atom.
  • For example, stable helium atoms exist that contain either one or two neutrons, but both atoms have two protons.
  • These different types of helium atoms have different masses (3 or 4 atomic mass units), and they are called isotopes.
  • Chlorine consists of two major isotopes, one with 18 neutrons (75.77 percent of natural chlorine atoms) and one with 20 neutrons (24.23 percent of natural chlorine atoms).
  • The atomic number of chlorine is 17 (it has 17 protons in its nucleus).

• Early Ideas about Atoms

  • In 1661, Boyle presented a discussion of atoms in his The Sceptical Chymist.
  • Dalton's experiments with gases led to some of the earliest measurements of atomic masses and a concept of atomic structure and reactivity.
  • Dalton's atomic theory contained the following ideas:
  • Atoms are indestructible.
  • Describe the early developments leading to the modern concept of the atom

• Electric Charge in the Atom

  • 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.

• The Thomson Model

  • 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.

• Atomic Theory of Matter

  • 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).

• Multielectron Atoms

  • 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.