For the Halogen Family, How Many Electrons Are in the Outermost S Orbital

The five elements; Fluorine (F), Chlorine (Cl), Bromine(Br), Iodine (I) and Astatine (At) belonging to VII A Grouping of the mod periodic table are collectively referred as halogens. The final element Astatine is radioactive and is very brusque lived hence generally excluded from the report.

The word halogen is derived from the Greek words Halos (Body of water Salt) and Genes (Producer). Since the binary compounds of halogen are the most abundant soluble salts found in the body of water. Thus element of group vii means salt producers.

Electronic Configuration of Halogens:

Sr.No.	Elements	Diminutive No.	Electronic    Configuration	Configuration   of valence crush
1	Fluorine (F)	9	ii, vii	2s2 2p5
2	Chlorine(Cl)	17	2, viii, 7	3sii 3pv
3	Bromine(Br)	35	two, eight,18, seven	4s2 4pfive
four	Iodine (I)	53	ii, viii, 18, 8, 7	5sii 5pv
v	Astatine (At)	85	2, 8, eighteen, 32, 18, 7	6stwo 6p5

Characteristic Electronic Configuration of Halogens:

• All halogens incorporate 7 electrons in their outermost crush. All other shells are completely filled. They accept feature outer orbit configuration of ns2 np5.
• The last electron during configuration occupies p orbital, hence these elements are p block elements.
• All orbits except the last orbit are completely filled. Hence they are normal elements.
• All halogens contain seven electrons in their outermost trounce. Hence they are kept in grouping Vii-A (17) of a periodic table, before inert gases.
• There are seven electrons in the outermost shell. So these elements require only 1 electron to complete the octet.

Properties of Halogens:

Monovalency of Halogens:

All halogen have shell electronic configuration is ns2 np5. They contain seven electrons in the valence shell. They demand i electron to consummate their octet. They reach the octet either by accepting an electron to form a univalent anion,  X-, (F-, Cl-, Br- and I-) by sharing the unpaired electron with the unpaired electron of another atom to grade a covalent bond (as in Cl2, Br2, HCI, HF etc).  Therefore, the common valency of halogen family unit is 1. Hence they are monovalent.

Atomic Radius:

Atomic and ionic radius is the distance from the middle of the nucleus to the outermost shell of the cantlet or ion. From fluorine to iodine atomic radius increases because of post-obit reasons.

Tendency: As we go down in the group diminutive radius increases from fluorine to iodine.

Caption:Equally we go down in the group

• Atomic number and number of shell increases.
• Effective nuclear accuse decreases.
• Screening effect increases.

It is to be noted that every ion is larger in size than the corresponding atom.

Oxidation State:

The characteristic electronic configuration of the halogens is ns2 np5. Hence, they tend to gain i electron to grade the stable electronic configuration of the nearest noble gas atom and exhibit – i uniform oxidation state.

Chlorine, bromine and Iodine have empty n-'d' orbital. These elements when combining with the more electronegative element, their electrons of nth orbit get promoted to n-'d' orbital. Therefore, they can show positive oxidation states like +1, +3, +5 and +7.

Fluorine has only -1 oxidation state due to the absence of vacant due north-'d' orbitals.

Fluorine has Only -1 Oxidation State:

Fluorine is the most electronegative element having highest electronegativity 4. It does non accept 'd' orbitals in Its valence trounce. So information technology cannot expand the octet. Hence fluorine has only –i oxidation land.

Ionization Potential (I.P.) or Ionization Enthalpy:

The energy required to remove outermost electron from the gaseous cantlet of an element, when it is in the basis country is chosen ionization potential or ionization enthalpy.

Since atomic radii of halogens are smallest in their corresponding catamenia, their ionization potentials are very loftier. They have no trend to lose the electron.

Among halogens, the I.P. (I.E.) value decreases with Increase in size of atom i.e. from fluorine to iodine. Therefore, the not-metallic backdrop decrease from fluorine to Iodine. Iodine is solid with metal lustre.

Fluorine has Highest Ionization Enthalpy:

Ionisation potential is the minimum energy required to remove most loosely bound  electron from the outermost shell of an isolated gaseous atom. Fluorine has high. I.P. due to post-obit reasons.

• Information technology has the smallest diminutive size
• The concluding electron present in 2p-orbital, which is nearer to the nucleus.

Therefore the last electron is held more than tightly past the nucleus, due to greater nuclear accuse. Thus more amount of free energy is required to remove that electron and I.P. is more than.

Electronegativity (EN):

The relative trend of the bonded atom in a molecule to attract the shared electron pair towards itself is termed as its electronegativity.

Amidst the elements in the same menstruation, halogens are nigh electronegative due to high nuclear accuse and small diminutive size. Their electronegativity and non-metallic character subtract gradually down the group with the increase in their atomic size. Electronegativity values are equally follows F = 4,  Cl = 3, B r = 2. eight, i = ii. v   (Notation: Oxygen electronegativity is 3.51)

Fluorine Evidence High Electro-negativity:

Electro-negativity is the trend of an atom to concenter shared electrons towards itself in a molecule. Fluorine has high electro-negativity due to following reasons

• It has the smallest atomic size.
• The terminal orbit is 2nd which is nearer to the nucleus and has a greater nuclear charge.

Therefore, the distance between the shared pair of electrons and nucleus of fluorine is small. Thus it has more ability to concenter the shared pair of electrons towards itself and electro-negativity is more.

Electron Affinity (EA):

Electron affinity is the free energy released when an electron is added to neutral gaseous atom forming a univalent negative ion. When halogens get electrons they surrender free energy.

Each halogen has maximum electron affinity in a period merely in halogen family, information technology decreases from fluorine to iodine. The guild of electron affinity is, Cl >  F> Br > I. Information technology tin can be explained as follows

• Atomic size increases
• Constructive nuclear charge decreases
• Power to attract electron decreases
• Screening effect increases

Electron Affinity of Fluorine is less than that of Chlorine:

Electron affinity is the energy released when an electron is added to neutral gaseous atom forming a univalent negative ion. The electron analogousness of fluorine is less than that of Chlorine. It tin can be explained as follows.

• Fluorine has an extremely small atomic size.
• 2p sub-shell is meaty in fluorine.
• The maximum chapters of the outermost orbit in fluorine is eight electrons only.

Due to to a higher place reasons, the added electron comes too shut to other valency electrons and this increases electron-electron repulsion. This results liberation of less free energy when fluorine atom receives electron and forms F- Ions.

Bond Dissociation Free energy (Bond Dissociation Enthalpy):

Bond dissociation free energy is defined every bit the energy required to suspension a particular bond into atoms.

In general, halogens are diatomic molecules in which covalent bond is formed by overlapping of 'p' orbitals. Since diminutive size increases from chlorine to Iodine, bond length increases from chlorine to iodine. As bail length increases from Cl to I. Bond dissociation energy decreases from chlorine to Iodine molecule.

Bond Dissociation Free energy of Fluorine is Exceptionally Less:

Bond dissociation energy is the free energy required to interruption the bond between the atoms in a gaseous molecule. Bond dissociation energy of F-F bond in F2 is less than Cl2, Br2 because of the following reasons

Fluorine has small diminutive size and in fluorine, 2p subshell is meaty and close to the nucleus.  Due to small atomic size number of electrons are held in a meaty volume and there is potent repulsion amongst non bonded electrons. Hence bond becomes weak though bail is brusque.  Due to this reason bond dissociation energy of fluorine less than other halogens.

Multiple bonding takes place in Cl2, Br2, I2, due to the presence of d-orbitals, while such blazon of multiple bonding is absent in fluorine due to the absence of d-orbitals.  Hence bond dissociation energy is loftier for other halogens.  The club of bail dissociation energy is, Cl2 > Br2 > F2 > I2

Bond dissociation energy of fluorine molecule is much less than that of chlorine molecule.

This is considering, in fluorine molecule, ii fluorine atoms are quite close together (i.eastward. F-F bond length is very short) due to full size of fluorine atoms. This gives rise to very strong repulsion betwixt the not-bonding electrons of the two atoms. The F-F bond, therefore, becomes weak.

In chlorine molecule, the repulsion is considerably minimised by longer Cl-Cl bond length due to the bigger size of the chlorine atoms.

Full general Properties of Halogens:

• Country: Fluorine and Chlorine are gases, bromine is liquid and iodine is solid.
• Colour: All are coloured and the intensity of colour increases from fluorine to Iodine. Fluorine is light yellow/Pale yellow gas. Chlorine is greenish-yellow gas. Bromine is scarlet-brown or Orange-red liquid and Iodine is violet or Shining black solid.
• Melting and Boiling Points: The elements have low boiling and melting points as their molecules are held together past Weak Vander Wall's forces. These forces become stronger with an increment in atomic size. So boiling and melting points increase from fluorine to Iodine. Thus, fluorine and chlorine are gases, bromine is volatile liquid and Iodine is solid, which easily sublimes.
• Oxidizing Property: Halogens are potent oxidizing agents. Fluorine is the well-nigh powerful oxidizing agent. Oxidizing power decreases from fluorine to iodine.

Fluorine is the most powerful oxidizing agent:

• Fluorine has smallest atomic size.
• Fluorine has the highest electronegativity (= 4)
• F-F bond dissociation energy is very low.
• Fluorine atom accepts electron readily to class F- ion. Hence it has high reduction potential Eo Ruddy = +ii.87 Volt.

Reasons for Anomalous Behaviour of Fluorine:

Fluorine differs from other halogens due to following reasons

• Smallest atomic size.
• Highest electronegativity.
• Weak F-F bond i.due east. F—F bond dissociation energy is depression.
• Non-availability of Id' orbitals in its valence shell.
• Strongest oxidizing agent (stronger than oxygen)

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Source: https://thefactfactor.com/facts/pure_science/chemistry/inorganic-chemistry/halogens/11354/

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