Group 17 Elements

Introduction to Group 17 Elements

Group seventeen elements include fluorine, chlorine, bromine, iodine and astatine.

Fig. 1: Group 17 elements

These elements are on the whole alluded to as the "halogens" as they react with metals to give salts.

Electronic Configuration

ns² np⁵ is the valence shell electronic configuration of these elements which makes clear why there are seven electrons in the outer shell.

Fig. 2: Electronic configuration of group 17 elements

The valence shell is short of an octet configuration by one electron. As these elements require one electron to achieve stable octet or closest ideal gas configuration, they have a strong inclination to either increase one electron to shape an ionic bond or impart an electron to another atom to frame a covalent bond.

The halogens constitute the most reactive group of non-metals. The high reactivity of the halogens is credited to their strong inclination to pick up or share an electron to accomplish closest inert gas configuration.
 

Occurrence

Inferable from their high reactivity, the halogens do not exist in Free State, yet in the consolidated state in nature, aside from astatine.

Astatine is radioactive in nature.

Fluorine is the 13^th and chlorine the 20^th most rich element by weight in the crust of the world.

Fluorineexist broadly as insoluble fluorides, for example, cryolite(Na3AlF6), fluorspar(CaF2), and fluoroapatite (Ca5(PO4)3F). Of these, the primary source is fluorspar. Little measures of fluorine are available in soil, plants of stream water, and the bones and teeth of creatures.

Chlorine, bromine, and iodine are available in ocean water as chlorides, bromides, and iodides of profoundly dynamic metals like sodium, potassium, magnesium and calcium. Of these, the richest is sodium chloride. Ocean water comprises around 1.5 % by weight of sodium chloride.

The dry beds of oceans additionally contain vast stores of sodium chloride alongside littler extents of calcium chloride and carnallite (KCl.MgCl2.6H2O).

Iodides are found in trace amounts in ocean water. The primary wellspring of iodine is ocean weeds and crude chile salt petre.
 

Atomic Properties

Patterns of a portion of the atomic properties of group 17 elements:

Atomic properties incorporate ionic and atomic radii, electron gain enthalpy, ionization enthalpy, and electro-negativity.
 

Trend of Ionic and Atomic Radii

As we move down the group, the nuclear radii, and ionic radii increment because of the addition of another vital energy level in each progressive element.

These elements have the smallest atomic radii when contrasted with different elements in the relating periods. This is a direct result of greatest powerful atomic charge.

Fig. 3: Trends in atomic and ionic radii

Ionisation Enthalpy

These elements demonstrate high estimations of ionization enthalpy. As an outcome, the molecules of these elements tend to lose electrons and frame positive particles. As we move down the group, the value of ionization energy diminishes. This is because of the steady increment in the nuclear size, which decreases the drive of fascination between the valence electrons and the core.

The ionization enthalpy of fluorine is considerably higher than any other halogen, which is ascribed to its little size.

Fig. 4: Ionization enthalpy of group 17 elements

Electron Gain Enthalpy

Halogens have the most extreme negative electron pick up enthalpy in the particular time frames.

The electron gain enthalpy turns out to be less negative on moving down the group.

Fluorine has less negative electron pick up enthalpy than chlorine. I.e. chlorine has the most extreme negative electron pick up enthalpy among every one of the elements. It is a result of the small size and reduced 2p sub-shell of the fluorine atom. Attributable to the small size of the fluorine particle, the approaching electron encounters a more noteworthy measure of repulsion from the electrons that are now present. The electron-electron repulsion between the approaching electron and the electrons officially introduced exceed the magnetism between the additional electron and the nucleus.

Electro-Negativity

The halogens have high electro-negativity values. You can see from the estimations of electro-negativity in the table that the electro-negativity diminishes slowly on moving down the group from fluorine to iodine because of the relative increase in the nuclear radii.

Fluorine, in the periodic table, is the most electronegative element.

Fig. 5: Electronegativity of group 17 elements

Physical Properties and Oxidation States

Group 17 elements are called halogens.Halogens are the most electronegative elements in the periodic table.
Physical Properties

Physical properties includephysical state, color, solubility, metallic character, density, melting and boiling point, bond dissociation energy.
Physical state:The group 17 elements exist in various physical state
F,Cl are gases
Br is a liquid
I is a solid
All these are diatomic in nature.

Color:  These elements displays diverse colors
F→ Pale yellow color
Cl → Greenish yellow color
Br → Reddish brown color
I → Dark violet color
Solubility:  F, Cl are soluble in water
Br, I are sparingly dissolvable in water yet totally dissolvable in organic solvents.

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Group 17 Elements