[Chemistry Class Notes] on The P-Block Elements: Group 17 Elements Pdf for Exam [2024]

The elements of the group 13 – 18 come under the p – block elements. In these elements the last electron enters in the outermost p – orbital. They have ns2np1-6 electronic configuration in the valence shell, helium being an exception. These elements show the maximum oxidation state equal to the sum of electrons in the outermost shell or valence shell. Most of the elements of the p – block form covalent compounds although some elements form ionic compounds (such as halogens) and coordination compounds as well.

p-block contains elements which are either metals, non – metals or metalloids. p-block elements include the group of halogens and inert gases. First member of each family of the p-block elements is given below in the table with their general electronic configuration and oxidation states. p-block has the most electronegative element which is fluorine. Elements of p-block generally form acidic oxides. Many elements such as C, Si, Ge, O, N etc. also show phenomenon of allotropy. Property of catenation is also shown by many elements.

Group 17 has a total of five elements such as fluorine, chlorine, bromine, iodine, and astatine. While the initial four are highly reactive and used in a variety of compound formations the last one is a radioactive substance. The entire group 17 is named as halogens in general as they tend to react with metals to produce salts. They consist of 7 electrons in their last shell.

They are just one electron short to become noble gases which are fulfilled by pairing with other metals. The high reactivity of halogens is what allows them to react with a huge number of elements. It is also seen that in the P-Block Elements: Group 17 Elements there is a metallic nature that increases as we move down the group.

Group	13	14	15	16	17	18
First Member of the Group	B	C	N	O	F	He
General Electronic Configuration	ns2np1	ns2np2	ns2np3	ns2np4	ns2np5	ns2np6
Group Oxidation State	+3	+4	+5	+6	+7	+8

We have covered the Boron Family (Group -13 elements), the Carbon Family (Group – 14 elements), the Nitrogen Family (Group – 15 elements), and the Oxygen Family (Group – 16 elements) in other articles based on p-block elements. In this article, we will cover the Halogen Family or Group 17 Elements of p-block elements (Class XII, Chemistry).

Group 17 Elements: The Halogen Family

Group 17 is the fifth group of p-block elements. The word Halogens is made up of two Greek words Halo and genes. Halo means salt and genes mean born, thus halogen means salt producers. All elements of group – 17 produce salts reacting with alkali metals or alkali earth metals. That’s why this group is also known as the Halogen family and these group elements are called halogens.

Elements of the Group – 17
Atomic number	Symbol	Metal/Nonmetal/Metalloid	Color & State	Electronic Configuration	Density g/cm3 at 298 K	Atomic and Ionic Radii	Ionization Enthalpy
9	F	Nonmetal	Pale yellow colored Gas	He He 2s2 2p5	1.5	Increases in moving from top to bottom in the group due to an increase in the number of shells.	Decreases on moving from top to bottom in the group due to a gradual increase in the size of elements.
17	Cl	Nonmetal	Pale yellow-green colored gas	Ne Ne 3s2 3p7	1.66
35	Br	Nonmetal	Reddish – brown Liquid	Ar Ar 3d10 4s2 4p5	3.19
53	I	Nonmetal	Metallic gray (Lustrous) solid	Kr Kr 4d10 5s2 5p5	4.94
85	At (Radioactive element)	–	–	Xe Xe 4f14 5d10 6s2 6p5	–
117	Ts (Synthetic Chemical element)	–	–	Rn Rn 5f14 6d10 7s2 7p5

Elements of the Group 17 – Physical Properties
Symbol	Atomic Number	Atomic Mass (g mol-1)	Melting Point (K)		Boiling Point (K)		Density	Ionic Radius	Electronegativity
F	9	19	54.4	Increases on moving from top to bottom in the group	84.9	Increases on moving from top to bottom in the group	Increases on moving from top to bottom in the group	Increases in moving from top to bottom in the group.	Decreases on moving from top to bottom in the group. Fluorine is the most electronegative element.
Cl	17	35.45	172		239
Br	35	79.90	265.8		332.5
I	53	126.90	386.6		458.2
At (Radioactive element)	85	210	–		–

Elements of the Group 17 – Chemical Properties
Oxidation Number	Group -17 elements generally exhibit only a -1 oxidation state.	Other than -1 oxidation state Cl, Br, I exhibit +1, +3, +5, and +7 oxidation states.	The oxidation states of +4 and +6 occur in the oxides and the oxoacid of chlorine and bromine.
Reactivity Towards Oxygen	All elements of the halogen family form oxides but most of these oxides are unstable in nature.	Fluorine forms two oxides OF2 and O2F2.	As we move down the group, the stability of halogen oxides decreases.
Reactivity with Hydrogen	All elements of the halogen family react with hydrogen and form hydrogen halides. Although as we move down the group stability of these halides decreases.	As we move down the group, the affinity for hydrogen decreases. H-X bond dissociation enthalpy order of halogens – H–F > H–Cl > H–Br > H–I	The acidic character of the hydrides of group 17 elements increases on moving down the group as the bond enthalpy of the H-E bond decreases on moving down the group. HF < HCl < HBr < HI
Reaction Towards Metal	All elements of the halogen family react with metals and form metal halides.	The ionic nature of metal halides decreases as we move down the group. MF > MCl > MBr > MI M = any monovalent metal	The halides in a higher oxidation state will be more covalent than the ones in the lower oxidation state. Such as SnCl4 is more covalent in nature than SnCl2.

Anomalous Properties of Fluorine

Fluorine differs from other elements of the group – 17 due to its high electronegative character, small size, low F-F bond dissociation enthalpy, and high ionization enthalpy.
Fluorine mostly shows exothermic reactions.
It forms only one oxoacid while other elements of the group – 17 form many oxoacids.
Hydrogen fluoride is liquid while other hydrogen halides are gases. fluorine forms a very strong bond with hydrogen due to its small size and high electronegative nature.
d- orbitals are not found in the valence shell of the fluorine atom.

Chlorine

Chlorine – Group – 17 element: Preparation, Properties, and Uses

Discovery

Preparation

Properties

Uses

Cl was discovered by Scheele in 1774. It was named by Davy in 1810.

The name comes from the Greek word chloros which means greenish yellow.

🡪 By heating manganese oxide with HCl.

Reaction –

MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O

🡪 By the reaction of hydrogen chloride and potassium permanganate.

Reaction –

2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2

🡪Deacon’s process – In this process, oxidation of HCl is done by atmospheric O2 in presence of catalyst cupric chloride at 723 K temperature.

Reaction –

4HCl + O2 CuCl2→ 2Cl2 + 2H2O

🡪 Electrolytic process – Chlori
ne can be obtained by the electrolysis of brine solution or conc. NaCl solution.

🡪 Pale yellow-green-colored gas has a pungent smell.

🡪 It has a suffocating odor.

🡪 It is heavier than air.

🡪 It easily reacts with various metals and forms metal chloride.

2Al + 3Cl2 → 2AlCl3

2Fe + 3Cl2 → 2FeCl3

🡪 It is soluble in water.

🡪 It reacts with hydrogen and compounds containing hydrogen. For example –

H2 + Cl2 🡪 2HCl

🡪 It produces a mixture of chloride and hypochlorite with cold and dilutes alkalies.

2NaOH + Cl2 → NaCl + NaOCl + H2O

🡪 It reacts with hydrocarbons. With saturated hydrocarbons, it gives substitution products while unsaturated hydrocarbons, it gives addition products.

🡪 It is used for bleaching textiles, cotton cloths, and wood pulp.

🡪 In many disinfectants, pesticides, etc.

🡪 It is used in the manufacture of various drugs and organic compounds.

🡪 It is used in sterilizing drinking water.

It bleaches vegetables and other organic matter in presence of moisture.

Cl2 + H2O → 2HCl + O

Colored substance + O → Colorless substance

🡪 It is used in the preparation of phosgene, tear gas, and mustard gas.

Hydrogen Chloride

Chlorine – Group – 17 element: Preparation, Properties and Uses

Discovery

Preparation

Properties

Uses

It was discovered by Glauber in 1648. Then in 1810, Davy showed that it is a compound of chlorine and hydrogen.

🡪 Laboratory method – It is prepared by heating NaCl with conc. sulphuric acid at 420 K temperature.

NaCl + H2SO4 🡪 NaHSO4 + HCl (420 K)

NaHSO4 further reacts with sodium chloride and forms Na2SO4 and HCl.

NaHSO4 + NaCl 🡪 Na2SO4 + HCl

🡪 It is a gaseous compound that has a pungent smell.

🡪 Its boiling point is 189 K.

🡪 Its freezing point is 159 K.

🡪 In a liquid state, it is colorless.

🡪 It is highly soluble in water.

HCl + H2O 🡪 H3O+ + Cl–

🡪 It is a strong acid.

🡪 Its mixture with conc. nitric acid is called aqua regia. In aqua regia, one part of conc. HNO3 and three parts of conc. HCl are mixed.

🡪 It reacts with ammonia and gives white fumes of ammonium chloride.

Reaction –

NH3 + HCl → NH4Cl

🡪 Its mixture of aqua regia is used for dissolving many metals.

🡪 It is used in the manufacture of chlorine, glucose, and ammonium chloride.

🡪 It is used as a laboratory reagent.

🡪 It is used in manufacturing medicines.

Oxoacids of Halogens

An oxoacid is an acid that contains oxygen. Oxoacids of halogens contain oxygen, hydrogen, and halogen atoms. For example, HOF, HOCl, HOBr, HOI, etc.

Fluorine forms only one oxoacid which is HOF due to its high electronegativity and small size.

Most of the oxoacids of halogens are not stable. They are stable either in an aqueous solution or in the form of their salts. The structure of few oxoacids of chlorine are given below –

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Interhalogen Compounds

Interhalogens compounds are those compounds that are formed by the reaction of two different halogens. They can be assigned general compositions as XX′, XX3′, XX5′, and XX7′ where X is larger size halogen and X′ of smaller size and X is more electropositive than X′. As the ratio between radii of X and X′ increases, the number of atoms per molecule also increases.

Interhalogen compound: Preparation, Properties, and Uses

Preparation

Properties

Uses

By the direct reaction of two different halogens

Reaction –

Cl2 + F2 🡪 2ClF (At 437 K)

🡪 ClF is a colorless gas.

🡪 BrF is pale brown gas.

🡪 ClF3 is a colorless gas.

🡪 ClF5 is a colorless liquid.

🡪 BrF5 is also a colorless liquid.

🡪 They are all covalent and diamagnetic in nature.

🡪 these compounds are used as solvents mostly non-aqueous solvents.

🡪 Interhalogen compounds of fluorine are very useful fluorinating agents. For example, used for the production of UF6

They are just one electron short to become noble gases which are fulfilled by pairing with other metals. The high reactivity of halogens is what allows them to react with a huge number of elements. It is also seen that in the P
-Block Elements: Group 17 Elements there is a metallic nature that increases as we move down the group.

Fun facts about halogens

The name halogen arises from two Greek names Hals which means salt and gen which means to make.
Fluorine gas is highly dangerous and just breathing about 0.1 percent of it will kill a person.
Simple compounds which consist of halogens are called halides
Bromine has a very strong bad odor which gets its name from bromos which means stench in the Greek language.
The first element of group 17 that was found out was Chlorine.
Astatine even though radioactive has great uses in medicine.

This is all about the P-block elements and their physical and chemical properties. Follow the explanation given here in simple language to develop your concepts regarding these elements in the Periodic Table.

Group 17 Elements: The Halogen Family

Anomalous Properties of Fluorine

Chlorine

Hydrogen Chloride

Oxoacids of Halogens

Interhalogen Compounds

Fun facts about halogens

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