Note that there is no clear division between metallic and non-metallic character. Fluorine gas reacts explosively with many other elements and compounds, and is considered to be one of the most dangerous known substances. It is not found in nature as a free element. That is why elements whose atoms have the same number of valence electrons are grouped together in the Periodic Table. > The valence electrons are the electrons in the outermost electron shell of an atom. Since the noble gases are a special group because of their lack of reactivity, the element fluorine is the most reactive nonmetal. The number of electrons in an atoms outermost valence shell governs its bonding behaviour. The most reactive nonmetals reside in the upper right portion of the periodic table. Nonmetals tend to gain electrons in chemical reactions, and have a high attraction for electrons within a compound. In addition, the atomic radius increases going down a group, placing the outer electrons further away from the nucleus and making that electron less attracted by the nucleus. Since the ionization energy decreases going down a group (or increases going up a group), the increased ability for metals lower in a group to lose electrons makes them more reactive. The metallic character increases as you go down a group. Reactivity of metals is based on processes such as the formation of halide compounds with halogens, and how easily the element displaces hydrogen from dilute acids. For example, it is commonly asserted that the reactivity of alkali metals ( Na, K. Both factors are actually distinct, and both commonly depend on temperature. It appears to embody both thermodynamic factors and kinetic factors (i.e., whether or not a substance reacts, and how fast it reacts). For example, both magnesium and zinc can react with hydrogen ions to displace H 2 from a solution by the reactions: Mg (s) + 2 H + (aq) H 2 (g) + Mg 2+ (aq) Zn (s) + 2 H + (aq) H 2 (g. Reactivity is a somewhat vague concept in chemistry. Chlorine compound, sodium chloride (table salt) has been known by human civilizations since prehistoric times and evidence of use of rock salt have been found from as early as 3000. It was discovered as a distinct element in 1810. The top metals are more reactive than the metals on the bottom. Chlorine is one of the most reactive gases and belong to the halogen group of periodic table. (Credit: User:Mirek2/Wikimedia Commons Source: Commons Wikimedia, Periodic Trends(opens in new window) License: Public Domain) The activity series is a chart of metals listed in order of declining relative reactivity.
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