Atom (science): Difference between revisions
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== Structure of the Atom == | == Structure of the Atom == | ||
Atoms are made of a dense [[nucleus]] formed by the two [[nucleons]] (positively charged [[protons]] and zero charge [[neutrons]]) and surrounded by a much larger "cloud" of [[electrons]]. The number of protons contained in the nucleus determines the [[atomic number]] and in turn which [[element]] it is classified as. The number of neutrons further specifies the [[isotope]] number of that element. The number of electrons surrounding the nucleus is typically assumed to be equal to the number of protons in order to keep the entire atom electrically neutral. Atoms that are not neutral are called | Atoms are made of a dense [[nucleus]] formed by the two [[nucleons]] (positively charged [[protons]] and zero charge [[neutrons]]) and surrounded by a much larger "cloud" of [[electrons]]. The number of protons contained in the nucleus determines the [[atomic number]] and in turn which [[element]] it is classified as. The number of neutrons further specifies the [[isotope]] number of that element. The number of electrons surrounding the nucleus is typically assumed to be equal to the number of protons in order to keep the entire atom electrically neutral. Atoms that are not neutral are called [[ions]], they are designated by their [[charge]] in units of [[elementary charge]], which is equal to the negative of the number of surplus electrons present around the atom. Thus an atom with one extra electron is charged -1, and one missing is charged +1. | ||
The nucleus of the atom contains a high concentration of positively charged particles with no counter balancing negatively charged particles to keep it stable. In order to explain the existence of the nucleus scientists introduced the two [[nuclear forces]], the [strong force]] and the [[weak force]]. We now understand that the nucleus is held together by the [[residual strong force]] despite its significant positive charge. The electrons which surround the atom are [[electro-statically|electromagnetism]] attracted to the nucleus due to their negative charge. | The nucleus of the atom contains a high concentration of positively charged particles with no counter balancing negatively charged particles to keep it stable. In order to explain the existence of the nucleus scientists introduced the two [[nuclear forces]], the [strong force]] and the [[weak force]]. We now understand that the nucleus is held together by the [[residual strong force]] despite its significant positive charge. The electrons which surround the atom are [[electro-statically|electromagnetism]] attracted to the nucleus due to their negative charge. | ||
Most combinations of nucleons are inherently unstable and undergo a number of [[radioactive decays|radiation]] in order to form more stable nuclei. | Most combinations of nucleons are inherently unstable and undergo a number of [[radioactive decays|radiation]] in order to form more stable nuclei. In all of the common decays a particle is emitted from the nucleus in order to compensate for some instability in the atom. | ||
* [[Alpha decay]] | * [[Alpha decay]] most frequently occurs in atoms which are simply too big, atoms are limited in size because the [[residual strong force]] which holds them together only acts over very small distances so that the rate of electrostatic repulsion grows faster than the rate of strong attraction as the nucleus grows. Alpha decay emits an [Alpha particle]] which is denoted with the [[Greek]] letter α. | ||
* [[Beta+ decay]] | * [[Beta+ decay]] | ||
* [[Beta- decay]] | * [[Beta- decay]] | ||
Revision as of 06:21, 31 October 2007
An atom (from the Greek atomos, indivisible) is the smallest physical unit that can retain its chemical properties. While atoms were once thought to be the smallest instances of mass in the universe, we now know that they are made up of smaller subatomic-particles.
Structure of the Atom
Atoms are made of a dense nucleus formed by the two nucleons (positively charged protons and zero charge neutrons) and surrounded by a much larger "cloud" of electrons. The number of protons contained in the nucleus determines the atomic number and in turn which element it is classified as. The number of neutrons further specifies the isotope number of that element. The number of electrons surrounding the nucleus is typically assumed to be equal to the number of protons in order to keep the entire atom electrically neutral. Atoms that are not neutral are called ions, they are designated by their charge in units of elementary charge, which is equal to the negative of the number of surplus electrons present around the atom. Thus an atom with one extra electron is charged -1, and one missing is charged +1.
The nucleus of the atom contains a high concentration of positively charged particles with no counter balancing negatively charged particles to keep it stable. In order to explain the existence of the nucleus scientists introduced the two nuclear forces, the [strong force]] and the weak force. We now understand that the nucleus is held together by the residual strong force despite its significant positive charge. The electrons which surround the atom are electromagnetism attracted to the nucleus due to their negative charge.
Most combinations of nucleons are inherently unstable and undergo a number of radiation in order to form more stable nuclei. In all of the common decays a particle is emitted from the nucleus in order to compensate for some instability in the atom.
- Alpha decay most frequently occurs in atoms which are simply too big, atoms are limited in size because the residual strong force which holds them together only acts over very small distances so that the rate of electrostatic repulsion grows faster than the rate of strong attraction as the nucleus grows. Alpha decay emits an [Alpha particle]] which is denoted with the Greek letter α.
- Beta+ decay
- Beta- decay
- Gamma decay