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1800-102-2727Meena, a 10-year-old girl, and her pals were playing Kho-Kho in the schoolyard. Meena tripped and fell to the ground while attempting to catch one of her friends. She was bleeding and had cut wounds on her knees and elbows. Her pals escorted her to the PE instructor (P.E.T.) so she could complain about the situation. Meena was told by her teacher to remain calm. The instructor cleaned the cuts with water before applying a dark-brown solution. The bleeding ceased after being treated with the dark solution.
Do you recognise the dark-brown liquid?
Iodine tincture solution is what it is.
One of the elements of group 17, iodine, has numerous crucial uses. There are several uses for other Group 17 elements like fluorine, chlorine, and bromine. Fluorine is a key ingredient in toothpaste, whereas chlorine aids in the purification of water in swimming pools.
We will go through the main characteristics of group 17 elements in more detail and discover how the periodic table's trends change on this concept page.
TABLE OF CONTENTS
Group 17 Elements – Introduction
VII-A, a group of elements from the periodic table's p-block, includes the elements that make up Group 17 components. These highly reactive non-metal elements, including fluorine, chlorine, bromine, iodine, astatine, and tennessine, make up this group. These elements were given the term "halogen," which in Greek means "to produce salt," since they may interact with the element sodium to form salts.
These elements are grouped together as they are all extraordinarily reactive and have many chemical characteristics in common. However, some patterns may be seen in the group, distinguishing the elements. While the other elements in this category typically exist in mixed form, astatine and tennessine are radioactive elements that have been specially created.
Group 17 Elements – Electronic Configuration
The valence shell electronic configuration of all the group 17 elements is the same. The general representation is ns2 np5, where ‘n’ is the shell number.
Element |
Atomic number |
Electronic configuration |
Fluorine |
9 |
|
Chlorine |
17 |
|
Bromine |
35 |
|
Iodine |
53 |
|
Astatine |
85 |
|
Tennesine |
117 |
The outermost shell of halogen elements has 7 electrons, as may be shown from the electronic configurations of group 17 elements. It simply takes one more electron to stabilise their valence p-orbital. Halogens are extremely electronegative and reactive due to the high valency of their electrons. The last electron in group 17 elements enters the p-orbital, and is therefore placed in the p-block of the periodic table.
Physical state
At room temperature, halogens can be found in different states of matter. As covalent diatomic molecules, halogens are kept together by a weak van der Waals force of attraction, but as the molecular mass grows, so does this force, changing the physical state of halogens as one moves down the group. Iodine, astatine, and tennessine are solids, whereas fluorine and chlorine are gases, and bromine is a liquid.
Solubility
Due to their non-polar nature, halogens are typically insoluble in water. However, fluorine interacts with the water molecule to produce oxygen and ozone.
Due to their non-polar character, elements in this group such (Cl2, Br2, I2 are more soluble in organic solvents like carbon tetrachloride (CCl4), chloroform (CHCl3), etc.
Colour
Each element in this group has a different colour. The amount of energy released as an electron returns from a higher energy state to a lower energy level results in an electromagnetic wave that is visible to the human eye, which determines the colour of the elements. The colours of the elements of the halogen group are listed below (in the diatomic state).
Element |
Colour |
Fluorine |
Light-yellow |
Chlorine |
Yellowish-green |
Bromine |
Reddish-brown |
Iodine |
Deep violet |
Astatine |
Black |
Oxidation State:
Since all members of the halogen group have seven valence electrons and only require one additional electron to complete their respective shells when combining with the less electronegative element, all members of the halogen group generally exhibit the ( -1) oxidation state.
Since fluorine is the most electronegative element in the periodic table, and is in the second period, it does not have any free d-orbitals where valence electrons might be excited to exhibit numerous oxidation states. As a result, fluorine consistently exhibits the ( -1) oxidation state.
On the other hand, due to the availability of unoccupied d-orbitals in the valence shell, chlorine, bromine, and iodine can create compounds with higher oxidation states as well, such as +1, +3, +5, and +7.
An element's oxidation state also affects how well it may interact with other elements. In order to make salts, elements with an oxidation state of ( -1) can accept an electron from other elements.
From fluorine to astatine, the Group 17 elements' oxidation strengths weaken. Thus, fluorides, the compounds formed by fluorine, are the most stable.
Oxidation state |
Fluorine |
Chlorine |
Bromine |
Iodine |
-1 |
HF, NaF, MgF2, XeF4 etc. |
NaCl, MgCl2, HCl CaCl2 etc |
NaBr,HBr AgBr etc. |
NaI,HI, MgI2 etc. |
+1 |
No compound |
HClO, Cl2O etc |
HBrO, Br2O etc |
ICl, HIO etc |
+3 |
No compound |
ClF3 , HClO2 |
BrF3 |
ICl3 |
+4 |
No compound |
ClO2 |
BrO2 |
I2O4 |
+5 |
No compound |
HClO3 |
BrF5, HBrO3 |
HIO3 |
+6 |
No compound |
Cl2O6 |
Br3O8(2 bromine atoms are in +6 oxidation state and one bromine atom is in +4 oxidation state) |
No compound |
+7 |
No compound |
HClO4 |
No compound |
IF7, HIO4 |
Order of atomic size in group 17: F<Cl<Br<I
Order of ionic size (X-): F-<Cl-<Br-<I-
Order of ionisation enthalpy in the group 17: F>Cl>Br>I
Order of electron gain enthalpy in the group 17: Cl>F>Br>I
Note: The electron gain enthalpy value for group 17 elements is negative, indicating that energy is released when the electron is added to the valence shell of an isolated gaseous atom.
Electronegativity
Order of electronegativity in the group 17: F>Cl>Br>I
Atomic Volume and Density
Bond Dissociation Energy
Reduction Potential and Oxidising Nature
Reduction Half Reaction |
Standard Reduction Potentials, E°(Volt) |
2.87 V |
|
1.36 V |
|
1.09 V |
|
0.54 V |
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Q1. Which of the following is the most reactive element?
A. I
B. Cl
C. F
D. Br
Answer: C
Solution: Fluorine is the most reactive halogen, which is why it is also known as a super halogen. It is the most electronegative element in the periodic table with a value of 4.0 on the Pauling scale. This suggests that fluorine has a strong tendency to attract electrons and be reactive.
So, option C is the correct answer.
Q2. What is the general electronic configuration of halogens?
A. ns2np3
B. ns2np2
C. ns2np4
D. ns2np5
Answer: D
Solution: Since the valence shell of the elements in group 17 has seven electrons, their general electrical configuration is ns2np5, or , where n=2 to 6 . As a result, they have one less electron than the nearby inert gas configuration.
So, option D is the correct answer.
Q3. Which of the following is the correct order of dissociation enthalpies of halogens?
A.
B.
C.
D.
Answer: B
Solution: Due to an increase in atom size as we go down the halogen group from F to I , the enthalpy of dissociation reduces as the bond distance increases from F2 to I2 .
However, the enthalpy of the F-F bond dissociation is lower than that of the Cl-Cl bond and even lower than that of the Br-Br bond. This is because the electron-electron repulsions between the lone pairs of electrons in fluorine are extremely strong due to the small size of the F atom. The bond between the two fluorine atoms is weakened by the strong electron-electron interactions between their lone pairs of electrons.
Therefore, the correct order of dissociation enthalpies of halogens is .
So, option B is the correct answer.
Q4. What is the atomicity of the halogen molecules?
A. One
B. Two
C. Three
D. Four
Answer: B
Solution: In comparison to the closest inert gas, each halogen has one electron less. Halogens are hence extremely reactive elements. They easily establish covalent connections with other atoms by sharing their lone unpaired electron. As a result, all halogens are diatomic molecules.
So, option B is the correct answer.
Q1. Who discovered chlorine?
Answer: Carl Wilhelm Scheele heated HCl and MnO2 to create chloride in 1774. On the basis of its colour, Davy proposed the term chlorine (Greek: chloros = greenish-yellow) in 1810 and confirmed its elemental nature.
Q2. The halogens produce what kind of bonds?
Answer: Ionic and covalent bonds are formed by halogens. Halogens bond with non-metals through covalent bonds. Atoms share electrons in covalent bonds. Atoms that share comparable electronegativity form covalent bonds. For instance, halogens can combine with hydrogen to form covalent bonds that result in acids like hydrofluoric acid (HF) and hydrochloric acid (HCl).
The alkali metals in group 1 of the periodic table are particularly good candidates for forming ionic bonds with halogens. Since the two atoms in an ionic bond have significantly different electronegativities, one atom gives an electron to the other. For instance, sodium readily gives one to chloride to create sodium chloride or table salt. In this bond, chlorine has a negative charge and sodium has a positive charge; both have a complete outer shell.
Q3. What happens if a halogen is subjected to sunlight?
Answer: Hydrogen chloride gas is created when a chlorine and hydrogen mixture is exposed to light or a flame and explodes. Lighting a hydrogen jet and dropping it into a gas jar of chlorine can control this process. The formation of hydrogen chloride gas continues to occur as the hydrogen burns more slowly and uniformly.
Q4. HF is the only liquid among the other hydrides of halogen at room temperature. Why?
Answer: HF is the only liquid among the other hydrides of halogen at room temperature. The hydrogen bonds that form between the F atom of one molecule and the H atom of another molecule are what cause HF to have an unexpectedly high boiling point. This is the main reason of HF to exist liquid at room temperature.
Related Topics
Dinitrogen |
Group-14 elements |
Chemical properties of group-13 |
Fluorine |
Bleaching powder |
P-block elements |
Interhalogen compounds |
Oxoacids of halogen |