Explanation:
The most active group of nonmetals belong to the halogen family.
These include fluorine, chlorine, bromine, iodine and .
In the periodic table, they appear to the left of the noble gases on the right side of the table.
They are so reactive that they are never found in nature by themselves.
Chlorine. The most active nonmetal in any period is second to last (halogens), right before the noble gases.
Explanation:
Atoms tend to give electron (metals) or take them (nonmetals) to achieve a stable configuration such as a noble gas (like argon) already has. If taking just one electron makes the atom's electron configuration like a noble gas, you have an active nonmetal. That's what elements right before the noble gases like chlorine, called halogens (Greek for salt-formers) do.
The most active nonmetals belong to the halogen family, which sits to the left of the noble gases on the right side of the periodic table. The halogens are so reactive that they are never found in nature by themselves. The elements fluorine, chlorine, bromine, iodine and astatine make up the halogen family. Halogens have seven valence electrons, which means that they have seven electrons in their outermost shells. These valence
electrons are the cause of an element’s reactivity. The tendency of atoms is to fill this outermost shell to capacity to attain a stable arrangement of electrons. For example, the noble gases, which contain eight electrons in the outermost energy level, are extremely stable elements because they already have their full complement of electrons. In nature, the noble gases generally do not form compounds with any other element. All other elements need to find situations in which they can
either donate or receive electrons to achieve their full complement. Halogens, because they need one more electron to have a stable arrangement, generally try to grab electrons from other elements; therefore, halogens are considered electronegative elements. Halogens tend to form stable arrangements called diatomic molecules in which two of the same halogen element share an electron. Electron donors such as metals like to combine with halogens to make stable compounds. Sodium chloride,
ordinary table salt, is the result of a chemical reaction between the metal sodium and the halogen chlorine.
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Hint: Periodic table has eighteen groups and seven periods, all the groups are mainly classified as blocks. We have four blocks in the periodic table: s-block, p-block, d-block and f-block. First two groups are under s-block (alkali metals, alkaline earth metals) third to twelve are in d-block(transition metals), thirteen to eighteen in p-block, f-block are inner transition metals.
Complete answer:
Non-metals in periodic tables are present right to periodic tables. Group
thirteen to eighteen also known as p-block elements. Group seventeen is the most active group among non-metals. The first element of this group is Fluorine (F) followed by chlorine (Cl), bromine (B), iodine (I) and astatine (At).
This group is known as the halogen family as the salts of these elements are present in seawater. The reactivity of halogens is due to their low bond dissociation energy, high enthalpy of hydration, high electron affinity. Many compounds of these elements are used in
our daily lives. As they are very reactive, they are never found in native state in nature. They are present in many oxidation states.
Some essential compounds from this group are: HCl, NaCl, HBr etc.
Note:
Fluorine is the most electronegative element and it has some different properties from its group members. This is known as anomalous behavior which is due to very small size, low bond dissociation energy, high electronegativity, non-availability of d-orbitals in valence
shell. And also fluorine is the strongest oxidizing agent.
Learning Objectives
Non-metallic character is the ability to be reduced (be an oxidizing agent), form acidic hydroxides, form covalent compounds with non-metals. These characteristics increase with a larger nuclear charge and smaller radius, with no increase in shielding. The most active non-metal would be the one farthest up and to the right -- not including the noble gases (non-reactive.)
Hydrogen
Hydrogen has a 1s1 electron configuration and is placed above the alkali metal group. Hydrogen is a non-metal, which occurs as a gas (H2) under normal conditions.
- Its ionization energy is considerably higher (due to lack of shielding, and thus higher \(Z_{eff}\)) than the rest of the Group 1 metals and is more like the nonmetals
- Hydrogen generally reacts with other nonmetals to form molecular compounds (typically highly exothermic)
- Hydrogen reacts with active metals to form metal hydrides which contain the H- hydride ion:
\[2Na_{(s)} + H_{2(g)} \rightarrow 2NaH_{(s)} \label{7.8.1} \]
- Hydrogen can also lose an electron to yield the aqueous \(H^+_{(aq)}\) hydronium ion.
Group 16: The Oxygen Family
As we proceed down group 16 the elements become more metallic in nature:
- Oxygen is a gas, the rest are solids
- Oxygen, sulfur and selenium are nonmetals
- Tellurium is a metalloid with some metal properties
- Polonium is a metal
Oxygen can be found in two molecular forms, O2 and O3 (ozone). These two forms of oxygen are called allotropes (different forms of the same element in the same state)
\[3O_{2(g)} \rightarrow 2O_{3(g)}\;\;\; \Delta H = 284.6\; kJ / mol \label{7.8.2} \]
the reaction is endothermic, thus ozone is less stable that O2
Oxygen has a great tendency to attract electrons from other elements (i.e. to "oxidize" them)
- Oxygen in combination with metals is almost always present as the O2- ion (which has noble gas electronic configuration and is particularly stable)
- Two other oxygen anions are observed: peroxide (O22-) and superoxide (O2-)
Sulfur
Sulfur also exists in several allotropic forms, the most common stable allotrope is the yellow solid S8 (an 8 member ring of sulfur atoms). Like oxygen, sulfur has a tendency to gain electrons from other elements, and to form sulfides (which contain the S2- ion). This is particular true for the active metals:
\[16Na_{(s)} + S_{8(s)} \rightarrow 8Na_2S_{(s)}\label{7.8.3} \]
Note: most sulfur in nature is present as a metal-sulfur compound. Sulfur chemistry is more complex than that of oxygen.
Group 17: The Halogens
"Halogen" is derived from the Greek meaning "salt formers"
- Astatine is radioactive and rare, and some of its properties are unknown
- All the halogens are nonmetals
- Each element consists of diatomic molecules under standard conditions
Colors of diatomic halogens: (not flame colors)
- Fluorine: pale yellow
- Chlorine: yellow green
- Bromine: reddish brown
- Iodine: violet vapor
The halogens have some of the most negative electron affinities (i.e. large exothermic process in gaining an electron from another element)
\[X_2 + 2e^- \rightarrow 2X^-\label{7.8.4} \]
- Fluorine and chlorine are the most reactive halogens (highest electron affinities). Fluorine will remove electrons from almost any substance (including several of the noble gases from Group 18).
Note
The chemistry of the halogens is dominated by their tendency to gain electrons from other elements (forming a halide ion)
In 1992, 22.3 billion pounds of chlorine was produced. Both chlorine and sodium can be produced by electrolysis of molten sodium chloride (table salt). The electricity is used to strip electrons from chloride ions and transfer them to sodium ions to produce chlorine gas and solid sodium metal
Chlorine reacts slowly with water to produce hydrochloric acid and hypochlorous acid:
\[Cl_{2(g)} + H_2O_{(l)} \rightarrow HCl_{(aq)} + HOCl_{(aq)}\label{7.8}.5 \]
Hypochlorous acid is a disinfectant, thus chlorine is a useful addition to swimming pool water
The halogens react with most metals to form ionic halides:
\[Cl_{2(g)} + 2Na_{(s)} \rightarrow 2NaCl_{(s)}\label{7.8.6} \]
Group 18: The Noble Gases
- Nonmetals
- Gases at room temperature
- monoatomic
- completely filled 's' and 'p' subshells
- large first ionization energy, but this decreases somewhat as we move down the group
Rn is highly radioactive and some of its properties are unknown
They are exceptionally unreactive. It was reasoned that if any of these were reactive, they would most likely be Rn, Xe or Kr where the first ionization energies were lower.
Note
In order to react, they would have to be combined with an element which had a high tendency to remove electrons from other atoms. Such as fluorine.
Compounds of noble gases to date:
\(XeF_2\) \(XeF_4\) \(XeF_6\)
only one compound with Kr has been made
\(KrF_2\)
No compounds observed with He, Ne, or Ar; they are truly inert gases.