In chemistry, valence electrons are the electrons contained in the outermost, or valence, electron shell of an atom. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Valence electrons are important in determining how an element reacts chemically with other elements: The fewer valence electrons an atom holds, the less stable it becomes and the more likely it is to react. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called The reverse is also true, the more full/complete the valence shell is with valence electrons, the more inert an atom is and the less likely it is to chemically react with other chemical elements or with chemical elements of its own type. In English to be inert is to be in a state of doing little or nothing This is because it takes more transfer of energy(photons) to lose or gain an electron from or into a shell when that shell is more complete/full. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena
Valence electrons have the ability like electrons in inner shells to absorb or release energy(photons). This gain or loss of energy can trigger an electron to move/jump to another shell or even break free from the atom and its valence shell. When an electron absorbs/gains more energy(photons), then it moves to a more outer shell depending on the amount of energy the electron contains and has gained due to the absorption of 1 or more photons. (Also see: electrons in an excited state)
When an electron releases/loses energy(photons), then it moves to a more inner shell depending on the amount of energy the electron contains and has lost due to the release of 1 or more photons. Excitation is an elevation in energy level above an arbitrary baseline energy state
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The number of valence electrons
| Valence Electrons |
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| Helium atom model This helium (He) model displays two valence electrons located in its outermost energy level. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Helium is a member of the noble gases and contains two protons, neutrons, and electrons. History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J |
The number of valence electrons of an element is determined by its periodic table group (vertical column) in which the sup element is categorized. In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in With the exception of groups 3–12 (transition metals), the number within the unit's place identifies how many valence electrons are contained within the elements listed under that particular column. In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in
| Periodic table group | Valence electrons |
|---|---|
| Group 1 (I) (alkali metals) | 1 |
| Group 2 (II) (alkaline earth metals) | 2 |
| Groups 3-12 (transition metals) | 1 or 2* |
| Group 13 (III) (boron group) | 3 |
| Group 14 (IV) (carbon group) | 4 |
| Group 15 (V) (nitrogen group) | 5 |
| Group 16 (VI) (chalcogens) | 6 |
| Group 17 (VII) (halogens) | 7 |
| Group 18 (VIII or 0) (noble gases) | 8** |
* The count of valence electrons is generally not useful for transition metals. In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling Biological occurrences Beryllium's low aqueous solubility means it is rarely available to biological systems it has no known role in living organisms and when encountered In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in History Carbon, Tin, and Lead, are a few of the elements well known in the ancient world - together with Sulfur, Iron, See also Gold chalcogenides Periodic table Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity
** Except for helium, which has only two valence electrons. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical
Valence electrons in chemical reactions
The number of electrons in an atom's outermost valence shell governs its bonding behavior. In Chemistry, valence, also known as valency or valency number, is a measure of the number of Chemical bonds formed by the Atoms A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Therefore, elements with the same number of valence electrons are grouped together in the periodic table of the elements. The periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is As a general rule, the fewer electrons in an atom's valence shell, the more reactive it is. Group 1 alkali metals are therefore very reactive, with lithium, sodium, and potassium being the most reactive of all metals. Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling Lithium (ˈlɪθiəm is a Chemical element with the symbol Li and Atomic number 3 Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39
Every atom is much more stable, or less reactive, with a full valence shell. This can be achieved one of two ways: an atom can either share electrons with neighboring atoms, a covalent bond, or it can remove electrons from other atoms, an ionic bond. An ionic bond (or electrovalent bond) is a type of Chemical bond that can often form between Metal and Non-metal Ions (or Another form of ionic bonding involves an atom giving some of its electrons to another atom; this also works because it can end up with a full valence by giving up its entire outer shell. By moving electrons, the two atoms become linked. This is known as chemical bonding and serves to build atoms into molecules or ionic compounds. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Five major types of bonds exist:
- ionic bonds
- covalent bonds
- coordinate covalent bonds (also called dative covalent bonds)
- hydrogen bonds
- metallic bonds
Valence electrons and electricity
The valence electrons are also responsible for determining the electrical conductivity nature of an element. An ionic bond (or electrovalent bond) is a type of Chemical bond that can often form between Metal and Non-metal Ions (or A coordinate covalent bond (formerly also known as dative bond) is a description of Covalent bonding between two atoms in which both electrons shared in the bond come A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen Although the term metallic bond is often used in contrast to the term Covalent bond it is better to speak of metallic bonding, because this type of bonding is Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an Electric current. The number of valence electrons in the valence shell (the outermost shell) determine if a valence electron in that valence shell can easily break free or not. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. The valence electrons that move from valence shell to valence shell are called free electrons and are the elementary particles responsible for electric current. In Solid-state physics, the free electron model is a simple model for the behaviour of Valence electrons in a Crystal structure of a Metallic In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere.
The shells and sub-shells of an atom can contain only a maximum number of electrons per shell. This is the same for the valence shell. In order for free electrons to move easily from the valence shell of an atom to the valence shell of another atom the valence shell needs to contain as few valence electrons as possible, because the more valence electrons a valence shell contains, the more complete/full that valence shell is and the more complete/full a valence shell is with electrons, the harder it will be for a valence electron to break free from the valence shell and act as a free electron. This is because it takes more energy(photons) to break valence electrons loose from a valence shell when that valence shell is nearly complete/full. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena
The reverse is also true. It takes less energy(photons) to break valence electrons free from a valence shell when that valence shell is nearly empty. (Note: Photons are the elementary particles which are responsible for the electromagnetic force. In Physics, the electromagnetic force is the force that the Electromagnetic field exerts on electrically charged particles An electron can absorb or release photons after which it can jump to another shell. Whether or not an electron will jump to another shell depends on the amount of energy the electron has received from absorbing 1 or multiple photons or the amount of energy it loses when releasing 1 or multiple photons. )
So the more incomplete the valence shell of an atom is, the more easily valence electrons can move from the valence shell of one atom to the valence shell of another atom, the easier the material that consists of those type of atoms will conduct electricity.
Conductors are usually atoms that have the property to contain three or less valence electrons in their valence shell. In Science and engineering, a conductor is a material which contains movable Electric charges. Conductors conduct electricity well. Copper, aluminium, silver and gold are relatively good conductors. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 WikipediaNaming Silver (ˈsɪlvɚ is a Chemical element with the symbol " Ag " (argentum from the Ancient Greek: ἀργήντος - argēntos gen Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79
Insulators are usually atoms that have the property to contain five or more valence electrons in their valence shell. An insulator, also called a Dielectric, is a material that resists the flow of Electric current. Insulators conduct electricity relatively poorly in comparison to conductors.
Semiconductors are usually atoms that have 4 valence electrons. Semiconductors conduct electricity, however not as well as conductors, but also not as poorly as insulators. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that In terms of conductivity semiconductors are between conductors and insulators. Examples of semiconductors are Silicon and Germanium. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32
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