It includes Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te), Polonium (Po). They are also called chalcogens (ore forming elements) because these are involved in chemical formulas of the ores such as oxides, sulphides, tellurides.
Atomic Properties:
(i) Electronic Configuration:
Their general electronic configuration is ns2 np4.
(ii) Atomic and Ionic radii
Atomic and ionic radii increases down the group. The size of O is exceptionally small.
(iii) Ionisation enthalpy : Down the group, IE decreases due to increase in size. IE values of group 16 elements are much lower than those of group 15 elements. This is because group 15 elements have extra stable half-filled p-orbital electronic configuration
(iv) Electron gain enthalpy: They have high tendency to accept two e–’s to become stable and hence have large negative electron gain enthalpies. Electron gain enthalpy of oxygen is least negative in this group due to its small size resulting in large e–– e– repulsions in 2p-subshell due to which the incoming e–’s are not accepted with ease.
(v) Electronegativity :
Electronegativity value decreases down the group with increase in size. Oxygen is the second most electronegative element in the periodic table.
Physical Properties :
(i) O exists as a diatomic molecule while other elements exist as octaatomic solids.
(ii) O forms pπ–pπ double bonds while other elements do not.
(iii) S has stronger tendency for catenation than O (due to stronger S–S bonds compared to O–O bonds)
(iv) All elements of this group show allotropy
(v) M.pts. and B.pts. increases down the group with increase in atomic number.
Chemical Properties
(i) Oxidation states:
1) They show both negative and positive oxidation states.
2) The stability of – 2 O.S. decreases down the group.
3) Due to high electronegativity of O it shows only negative O.S. of –2 except in OF2 and O2F2 where it shows + 2 and +1 oxidation states respectively.
4) In peroxides like H2O2, O has – 1 oxidation states and in O2, it has zero oxidation states.
5) Other elements show +2, +4, +6 oxidation states.
6) S, Se, Te show +4 oxidation states with O and +6 with F.
7) Due to inert pair effect, stability of + 6 oxidation state decreases down the group while that of + 4 oxidation states increases.
8) Bonding in higher oxidation states, i.e. +4 and +6, is primarily covalent.
(ii) Reactivity with hydrogen :
1) They form hydrides of the type H2E.
2) Bond angle decreases from H2O to H2Te. This is because as electronegativity decreases from O to Te, electron density also decreases i.e. electron pair repulsion in electron pairs around the central metal atom decreases bond angle also decreases.
3) Their acidic character increases from H2O to H2Te. This is due to decrease in bond dissociation energy down the group. For the same reason, thermal stability of hydrides decreases from H2O to H2Po.
4) All hydrides except H2O possess reducing property and this character increases from H2S to H2Te. This is due to decrease in bond dissociation energy due to increase in bond length value.
(iii) Reactivity with oxygen:
1) Ozone is considered as oxide of oxygen O.
2) O3 and SO2 are gases while SeO3 is solid.
3) Reducing property of dioxides decreases from SO2 to TeO2, SO2 is reducing while TeO2 is an oxidising agent
(iv) Reactivity towards halogens:
1) They form a large number of halides of the type EX6, EX4, EX2.
2) Among hexahalides, hexafluorides are the only stable halides. All hexaflourides are gaseous in nature and have octahedral structure. SF6 is exceptionally stable due to steric reasons.
3) Among tetrafluorides, SF4 is a gas, SeF4 is a liquid and TeF4 a solid. They have sp3d hybridisation and see-saw geometry (with a lone pair at one of equatorial positions).
4) All elements except Se form dichlorides and dibromides which have sp3 hybridisation and tetrahedral structure.
5) Monohalides are dimeric in nature and undergo disproportionation.
Revision of NEET Chemistry The p-Block Elements is a crucial aspect of effective learning. Revision plays a vital role in the learning process and is especially important before exams. Here are some key points you can consider emphasizing in your content:
By highlighting the benefits and strategies of effective revision, you can approach your studies more mindfully and achieve better results in your exams. Best of luck bachhon!
NEET Chemistry seems to be a quite difficult subject for a lot of students. But, if you get a very good conceptual understanding of the subject, it can be very interesting for you.
We, at LearnoHub, will give our best to make NEET Chemistry The p-Block Elements NCERT Chapter 11 super-duper easy for you.
We aim at making learning fun as well as engaging for you with our complete end-end learning content with The p-Block Elements NEET Chemistry Best videos, Notes, NCERT pdf, NCERT complete syllabus, tests and Practice Questions.
Always remember, it is very important to study with full concentration during Revision. Here are a few tips for you on how to revise with full focus:
Remember, studying with full concentration is a skill that takes time and practice to develop. If you find your mind wandering during study sessions, gently bring your focus back to the task at hand and be patient with yourself. With consistent effort, you can improve your ability to concentrate and make the most of your study time.
Last but not the least, To get the best hold on NEET Chemistry The p-Block Elements Book Chapter 11. Do not forget to check out: