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| | Selling or buying jewelry requires huge amount of research and knowledge so that they can to obtain pieces that you want or need. This can make you wonder where to open.<br><br> |
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| '''Reactivity''' in chemistry refers to
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| * the chemical reactions of a single substance,
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| * the chemical reactions of two or more substances that interact with each other,
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| * the systematic study of sets of reactions of these two kinds,
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| * methodology that applies to the study of reactivity of chemicals of all kinds,
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| * experimental methods that are used to observe these processes,
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| * theories to predict and to account for these processes.
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| The chemical reactivity of a single substance (reactant) covers its behaviour in which it: | |
| * Decomposes
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| * Forms new substances by addition of atoms from another reactant or reactants
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| * Interacts with two or more other reactants to form two or more products
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| The chemical reactivity of a substance can refer to the variety of circumstances (conditions that include temperature, pressure, presence of catalysts) in which it reacts, in combination with the: | |
| * Variety of substances with which it reacts,
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| * Equilibrium point of the reaction (i.e., the extent to which all of it reacts)
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| * Rate of the reaction
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| The term ''reactivity'' is related to the concepts of ''[[chemical stability]]'' and ''[[Compatibility (chemical)|chemical compatibility]]''.
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| ==An alternative point of view==
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| ''Reactivity'' is a somewhat vague concept in chemistry. It appears to embody both thermodynamic factors and kinetic factors—i.e., whether or not a substance reacts and how fast it reacts. Both factors are actually distinct, and both commonly depend on temperature. For example, it is commonly asserted that the reactivity of group one metals (Na, K, etc.) increases down the group in the periodic table, or that hydrogen's reactivity is evidenced by its reaction with oxygen. In fact, the rate of reaction of alkali metals (as evidenced by their reaction with water for example) is a function not only of position within the group but particle size. Hydrogen does not react with oxygen—even though the equilibrium constant is very large—unless a flame initiates the radical reaction, which leads to an explosion.
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| Restriction of the term to refer to reaction rates leads to a more consistent view. ''Reactivity'' then refers to the [[Reaction rate|rate]] at which a [[chemical substance]] tends to undergo a [[chemical reaction]] in time. In pure [[chemical compound|compound]]s, reactivity is regulated by the physical properties of the sample. For instance, grinding a sample to a higher specific surface area increases its reactivity. In impure compounds, the reactivity is also affected by the inclusion of contaminants. In [[crystalline]] compounds, the crystalline form can also affect reactivity. However in all cases, reactivity is primarily due to the sub-atomic properties of the compound.
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| Although it is commonplace to make statements that substance 'X is reactive', all substances react with some reagents and not others. For example, in making the statement that 'sodium metal is reactive', we are alluding to the fact that sodium reacts with many common reagents (including pure oxygen, chlorine, hydrochloric acid, water) and/or that it reacts rapidly with such materials at either room temperature or using a bunsen flame.
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| 'Stability' should not be confused with reactivity. For example, an isolated molecule of an electronically state of the oxygen molecule spontaneously emits light after a statistically defined period. The half-life of such a species is another manifestation of its stability, but its reactivity can only be ascertained via its reactions with other species.
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| ==Causes of reactivity==
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| The second meaning of 'reactivity', that of whether or not a substance reacts, can be rationalised at the atomic and molecular level using older and simpler valence bond theory and also atomic and molecular orbital theory. Thermodynamically, a [[chemical reaction]] occurs because the products (taken as a group) are at a lower [[Thermodynamic free energy|free energy]] than the reactants; the lower energy state is referred to as the 'more stable state'. [[Quantum chemistry]] provides the most in-depth and exact understanding of the reason this occurs. Generally, [[electron]]s exist in [[molecular orbital|orbital]]s that are the result of solving the [[Schrödinger equation]] for specific situations.
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| All things (values of the ''n'' and ''m''<sub>l</sub> [[quantum numbers]]) being equal, the order of stability of electrons in a system from least to greatest is unpaired with no other electrons in similar orbitals, unpaired with all degenerate orbitals half filled and the most stable is a filled set of orbitals. To achieve one of these orders of stability, an atom reacts with another atom to stabilize both. For example, a lone [[hydrogen]] atom has a single electron in its 1s orbital. It becomes significantly more stable (as much as 100 [[calorie|kilocalories]] per [[mole (unit)|mole]], or 420 [[joule|kilojoules]] per mole) when reacting to form H<sub>2</sub>.
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| It is for this same reason that [[carbon]] almost always forms four [[chemical bond|bonds]]. Its ground state [[Valence (chemistry)|valence]] configuration is 2s<sup>2</sup> 2p<sup>2</sup>, half filled. However, the [[activation energy]] to go from half filled to fully filled p orbitals is so small it is negligible, and as such carbon forms them almost instantaneously. Meanwhile the process releases a significant amount of energy ([[exothermic]]). This four equal bond configuration is called sp<sup>3</sup> [[Orbital hybridisation|hybridization]].
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| The above three paragraphs rationalise, albeit very generally, the reactions of some common species, particularly atoms, but chemists have so far been unable to jump from such general considerations to quantitative models of reactivity.
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| ==Chemical kinetics: reaction rate as reactivity==
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| The rate of any given reaction,<br />
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| ''Reactants → Products''<br />
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| is governed by the [[rate law]]:
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| <math>Rate=k*[A]</math>
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| where the [[Reaction rate|rate]] is the change in the molar concentration in one second in the rate-determining step of the reaction (the slowest step), [A] is the product of the molar concentration of all the reactants raised to the correct order, known as the reaction order, and ''k'' is the reaction constant, which is constant for one given set of circumstances (generally temperature and pressure) and independent of concentration. The greater the reactivity of a compound the higher the value of ''k'' and the higher the rate. For instance, if,<br />
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| ''A+B → C+D''<br />
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| Then:
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| <math>Rate=k*[A]^n*[B]^m</math>
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| where n is the reaction order of A, m is the reaction order of B, n+m is the reaction order of the full reaction, and k is the reaction constant.
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| ==See also==
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| {{Wiktionary|reactivity}}
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| *[[catalysis]]
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| *[[Reactivity series]]
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| *[[Michaelis-Menten equation]]
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| *[[organic chemistry]]
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| *[[chemical kinetics]]
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| {{DEFAULTSORT:Reactivity (Chemistry)}}
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| [[Category:Chemical properties]]
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Selling or buying jewelry requires huge amount of research and knowledge so that they can to obtain pieces that you want or need. This can make you wonder where to open.
The chain is just one of the main attractions any kind of piece of necklace. The entire look will not be appreciated without the chain in your head. So tend to be your options in the Celtic-inspired design? The first one is the gold jewellery the appropriate approach . be carved out of pure gold or in combination with another metallic process. Some Celtic necklaces are also made from sterling jewelry. This is where fine silver jewellery is offered in.
For Friends: friends are those special people who share a bond beyond explanation. Substantial a wonderful source of joy, laughter and fun in your lives. Usually are your strong support in times of pain and trouble. Selection time could be there to honor these friends than Charismas? Friendship bands, bracelets, alphabet Pendants suite the occasion all right. As this bond is a very personal one, personalized gifts prove always be of great value. Send gifts in India like photos printed on mugs, calendars in addition to.
Round Brilliant - The round brilliant is modern day day version of the round using a lot more sparkle and shine. Individuals the trendiest choice in diamond bandz.
Emerald - The emerald is a regular shape which has step facets and clipped corners. It may be " old world " but its popularity increased when Tiffany first to sit down in a receptive setting upto a century within the. That way light could move across and it took the fact that once a drab cut to the level.
For men, low - cut shoes of silver and Grey shades are popular and stand out this trend. They express sophistication and relief in a sporty examine. For women, transparent or clear slippers tie at the some glittering silver provides somewhat a fairytale effect like Cinderella.
The twelve main gemstones and are each caused by a month of the entire year. Often these gemstones are referred to as birthstones. Below is did you know the the months and the stone in the neighborhood . associated with each month. It's a good idea by sentimental pieces to find a mother is to purchase gemstones that report to the months their kids were created.
Birthday card. While many people would believe the cost of the gift is essential for it with regard to remembered, nothing can match the memory of a simple message written on a card. Some may come across it cheesy but for her who values thought more than material things, it means a boatload.
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