why are iodine and astatine called extremely reactive?

Question

this is about chemical symbols

Answer 1

Hey:
I will attempt to anser your question:
The halogens are group 17 and they mean "salt formers". The halogens are made up of 5 elements :fluorine,chlorine,bromine, Iodine and Astatine.
Becoz they are chemically reactive none of them occur in the natural element form!
All of the five halogens are abudant except astatine, its very rare.
Now lets go to the chemistry of Iodine and Astatine:

Iodine is a solid whereas Astatine is radioactive and is one of the rarest of the chemical element!

Chemical reactivity decreaes as you go down the trend for halogens so Fluorine is most reactive and astatine least reactive!Becuse of the halogens reactivity they are extremely dangerous and thus they are given the corresponding chemical symbol!
. Iodine vapor is irritating to the eyes and respiratory system. It is highly toxic if ingested. Iodine is the least active of the common halogens (not counting astatine).

Iodine is also used commercially in a variety of products including dyes, specialized soaps, lubricants, photographic film, medicines, and pharmaceuticals.

Astatine
Astatine is generally regarded as one of the rarest naturally occurring elements.
About 24 isotopes (forms) of astatine exist, all of them radioactive. The most long-lived has a half-life of 8.3 hours, meaning that half of a sample of the element disappears in 8.3 hours. Because it is so rare and has such a short half-life, astatine is one of the most poorly understood of all chemical elements. It has no practical applications at this time.

Ps: These two halogens and all other halogens are extremely reactive and given the chemical symbol becoz halogens have seven electron in their outer atomic shell and they just need one more electon to have a filled shell so they can bond easily with alkaloids and acids to have complete shell!
Also when they bond they form the salt of some elements, thats becoz of their reacvtive nature!
Because of they are diatomic molecules they are not found free in nature but produced from halide salts.
The most obvious chemical property of halogen elements is their ability to act as oxidizing agents. The relative oxidizing ability of halogens corresponds to their order in the Periodic Table, F2 > Cl2 > Br2 > I2

1. Halogens comprise a highly reactive family of elements that do not exist in the free state in nature but can be prepared electrochemically or chemically from halide melts or halide solutions (see Laboratory Activity 1 and Demonstration 1).
2. Free halogen atoms (seven outer valence electrons) are one electron short of an eight-electron noble gas configuration. The atoms dimerize (2X ---> X 2 ) or act as very strong oxidants (X + e – ---> X – ) to complete the octet of electrons.

3. Diatomic halogens are fairly strong oxidants (X 2 + 2e– ---> 2X– ; with F2 > Cl2 > Br2 > I2 > At2 ). The reverse reaction can be obtained electrochemically or by stronger oxidizing agents. These reactive elements have characteristic properties, e.g., at room temperature they exist as gases (fluorine and chlorine), a liquid (bromine), and solids (iodine and astatine) with colors ranging from light and medium yellow-greens for fluorine and chlorine through deep red for bromine to almost black with a metallic lusterforiodine—although its vapor is a rich violet color (see Laboratory Activity 2 and Demonstrations 1b, 4).

4. Halide ions (X – ) have noble gas electron configurations and are found in nature as stable crystalline solids (salts), that, with few exceptions, are soluble in water, are colorless unless colored by the cation component, and are used to form strong acids (except fluoride).

5. Halogens, except fluorine, form oxoanions (XOn– ) that are highly reactive and can serve as bleaching agents and disinfectants similar to the elements themselves. Oxyhalogen ions provide another way for electron octet formation. These anions formally contain halogen atoms in positive oxidation states, which have even fewer valence electrons per halogen atom than in the free element. This is consistent with the fact that they are even stronger oxidants than are halogens.

6. Organic halogen compounds are rare in nature, although many useful and stable ones have been synthesized. They can be solids, liquids, or gases; some form very stable polymers. Halogens in these organics are covalently bonded
to carbon, making organic halogen compounds inert, except in the presence of irradiation, heat, or catalysts. Unfortunately, many are highly toxic, and the stability of others is causing environmental problems.

7. Halogen elements provide trends that can be extended elsewhere in the Periodic Table. These include, but are not limited to, trends in oxidizing strength, atomic and ionic sizes, completion of the octet of electrons by sharing electrons or forming anions or oxoanions, and trends in electronegativities .

I hope that answers your question!
Good luck!
Love SANAM

Answer 2

Both elements belong to the class of halogens, or "salt formers", and have an outer valence shell containing 7 electrons. This makes them extremely likely to bond with the alkaloids and alkalai earth metals in group IA and IIA, because it appears that having 8 electrons in the outer valence shell is the opitimum. The resulting ionic bond creates a crystaline form which is not limited in size because the cations and anions can attract more than one of each other, as long as they are combine in the fixed ration of the particular compound.