How to study gases that do not exist in nature? It is not as easy as you think. Fluorine is too reactive to be free in nature. Because halogens are highly reactive (unlike some metals such as gold and silver) they do not exist freely. Elemental fluorine reacts violently with other substances. Some elements are much more responsive than others. Elements from other groups have a much higher tendency to accept electrons during a reaction.
The term halogen is derived from the Greek meaning producers of salt because halo means “salts” and gene means “born”. Halogen group elements are extremely sensitive (reactive) to non-metallic elements. These elements show a subsequent gradual change in the physical and chemical properties of the elements.
The term “halogen” means “salt formation”. Halogen is a group of elements on the periodic table that share similar properties. It is the 17th group (according to IUPAC nomenclature) of the well-known periodic table of all elements known to the world. Currently, halogens are classified into five elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Tennessin (Ts), a new artificially created element 117, can also be a halogen family. These elements readily react with alkali and alkaline earth metals to form a wide range of salts such as calcium fluoride, silver bromide, potassium iodide and sodium chloride (common salt).
The arrangement of electrons of an atom in its orbitals for purpose of studying is called electronic configuration. It further helps one understand the trends in the physical and chemical properties of an element. It is important to know the number of electrons in the outermost shell of the element for the determination of the reactivity and types of bonds formed by an element that can be configured.
Pauli’s elimination principle is based on the quantum number defined by Pauli. He said that all four quantum numbers of two electrons in an atom can never be the same. According to Hund’s law, electrons form a pair in an orbital only after every subshell consists of at least one electron. According to the Aufbau principle, electrons in an element fill their energy levels in ascending order. The typical electronic configuration of a group 17 element is ns2np5. Seven electrons are found in their outermost shell. Hund’s Rule: Hund’s maximum multiplicity rule states that an electron can be truncated from an orbital only if all subshells consist of at least one electron. Aufbau’s Principle: According to this principle, electrons in any element can fill their energy levels in ascending order.
Halogen molecules have diatomic configuration and have seven valence electrons. Formation of negative ions that are highly reactive occurs. A property these groups of elements possess is gaining an electron on reaction with other elements. They do not exist in free state due to high reactivity, Fluorine being the most reactive elements to exist. Halogens have a strong and nasty smell and are highly toxic in nature. Besides being poor conductors of electricity and heat they furthermore have low melting and boiling points, this group contains elements in all three states of matter and it’s the only one too. They also react with alkali metals and alkaline earth metals to produce a wide range of salts.
Let’s look at the electronics of each halogen element individually. First, Fluorine (F), it is a pale-yellow diatomic gas at room temperature, highly toxic and highly corrosive. The atomic number is 9. It belongs to period 2 and is in block p. The electron configuration of fluorine is HeHe2s22p6. (Images will be uploaded soon) secondly, Chlorine (Cl) being greenish-yellow gas with a very strong odor. The atomic number is 17 and the p-block, period 3. The electronic configuration of this halogen is NeNe3s23p5. third Bromine (Br): At room temperature, bromine is a reddish-brown liquid with a sour odor. Period 4 and atomic number 35 located in the pblock have the same electronic configuration as ArAr3d104s24p5. fourth Iodine (I): Iodine gas vapor is purple. It has atomic number 53 and belongs to the 5th pblock period. Electronic configuration – KrKr4d105s25p5. 5. Astatine (At): Astatine is an unstable radioactive compound with atomic number 85. It belongs to the pblock, the 6th period of the periodic table, with the electron arrangement XeXe4f145d106s26p5.
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Summarizing the above concepts, the word “halogen” comes from the Greek “hal” meaning salt and “gen” meaning production, Fluorine gas is considered lethal. Inhaling air containing 0.1 microns of fluoride can be fatal. It is considered one of the most reactive elements that exist. Water and toothpaste contain small amounts of fluoride to prevent tooth decay. Astatine is a radioactive substance and although it decays very quickly, it has been shown to be used in medicine. Iodine is used to clean wounds and cuts because it acts as an antiseptic. Chlorine was the first halogen to be detected, isolated, and recognized as an element.