p block elements.
The article in your hand p block elements questions and answers primarily meant for graduate and postgraduate students of Chemistry with the intention that they could show better performance during various competitive examinations and interviews held for Civil and Military Services. At the same time it is equally useful for those who desire to be well informed in various disciplines of chemistry.
Q1. What are P-block elements?
Elements in which P-orbitals are in the process of filling in order to reach the inert gas configuration are called P block elements. The elements have completely filled ns orbitals and have np1-6 electronic configuration.
Q2. Which periodic groups belong to this block?
Groups IIIA, IVA. VA, VIA, VIIA and zero group belong to this block.
Q3. What is the nature of P-block elements?
Whereas s, d and f block elements are almost all metals, the P- block elements include metals non-metals, metalloids and inert gases.
Q4. How does electro negativity values vary in P-block elements?
The electro negativity values of P-block elements decreases down the group and increases in a period.
Q5. Discuss the electro positive character of P-block elements?
The electro positive character of P-block elements decreases on moving in a period, because ionization energy increases from left to right in a period and increases down the group due to decrease in ionization energy.
Q6. Why do P-block elements not give characteristic colour in the flame?
The reason is that the excitation energy given out by the electrons, when they come back to ground state, does not appear in the visible region of the spectrum.
Q7. What is the nature of chemical bonding in P-block elements?
Usually covalent bonding is present in P-block elements.
Q8. What is the nature of oxides formed by P-block elements?
We know that P-block elements include metals. metalloids and non-metals. The metallic elements of P-block give basic oxides (Bi2 O3), metalloids give amphoteric oxides (As2. O3 ) and non-metallic elements give acidic oxides (CO2, SO3).
Q9. Write the names of group IIIA elements.
Group IIIA of the periodic table consists of five elements which Are: Born (B), Aluminium (Al), Gallium (Ga), Indium (In) and Thallium (TI).
Q10. What is the valence-shell electronic configuration of group IIIA?
The valence-shell electronic configuration of group IIIA is ns2p1.
Q11. Why boron usually forms covalent compounds?
Since boron atom has small sire and high ionization energy, it does not lose all of its valence electrons and hence does not give B+ion. It is for this reason that boron atom combines with other elements through covalent bonds, i.e., boron atom mainly gives covalent compounds.
Q12. Discuss the metallic character of boron group.
All the members of this group are metals except boron which is semi-metal.
Q12. Why boron shows diagonal relationship with silicon?
Some common proportion showing the similarities between B and Si are given below:
- Both the elements can be prepared by reducing their oxides.
- Chemically, both the elements are typical non-metal and are bad Conductors of heat and electricity.
- Both the element are normally inert at room temperature.
- Boron and silicon combine with O2 at elevated temperature to form stable oxides, viz. B2O3 and SiO2.
Q13. How does boron differ from silicon?
The following points show dissimilarities between boron and silicon.
- Boron has three electrons in its valence shell while silicon has four electrons.
- Boron combines with N2. to give BN, while silicon does not combine with N2.
- Boron is tri-covalent in its compounds, while silicon is tetra covalent in its compounds.
- Boron is oxidized by hot cone HNO3 or hot cone H2SO4 to form H3BO3,while silicon is only attacked by HF.
Q14. Give some uses of boric acid.
Boric acid (H3 BO3), it is used
- In the manufacture of pottery glazes, glass and enamels.
- In medicine as an antiseptic and as an eye lotion.
- As preservative in food industry, and
- In the manufacture of borax and pigments.
Q15. Give some uses of borax.
Borax or sodium tetraborate (Na2 B4 O7O1OH2O) is a sodium salt of tetra boric acid (H2 B4O7). It is used:
- In borax bead test for the detection of basic radicals.
- In the manufacture of enamels and glazes for pottery
- In making optical glass and boro-silicate glass-ware.
- In the manufacture of washing powders and soaps.
Q16. Write the names of group IVA elements.
Group IVA of the periodic table consists of five elements viz. Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn) and Lead (Pb). Carbon is an essential constituent of all organic matter, while silicon is the main constituent of inorganic matter.
Q17. What is the valence shell electronic configuration of group IVA elements?
The valence shell electronic configuration of group IVA elements is ns’ p’.
Q18. How does carbon occur in nature?
Carbon is the only element of this group which occurs in the free state as diamond, graphite and coal.In the combined state, it occurs as hydrocarbons, carbohydrates and carbon dioxide in the atmosphere.
Q19. How does lead occur?
Lead occurs in mineral galena, PbS.
Q20. Discuss the metallic and non-metallic character of group IVA elements.
The first two elements, viz. C and Si are distinctly non-metals; the third element vs; Ge is partly a metal and partly a non-metal (i.e., metalloid), while the last two elements viz; Sn and Pb are distinctly metals.
Q21. What is catenation or self-linkage?
All the elements of group IVA have a tendency to link with each other and thus forms long chains of identical atoms. This type of linking of identical atom with each other is called catenation or self-linkage.
Q22. Give some uses of nitric acid.
It is used:
- in the manufacture of nitrate which are important chemicals of commerce. Basie calcium nitrate is used us fertilizer. Silver nitrate is used in photography and sodium nitrate in the manufacture of gunpowder and fireworks.
- in the manufacture of explosives like nitroglycerine, dynamite, trinitrotoluene, picric acid etc.
- in the manufacture of artificial silk, dyes and perfumes.
- in the manufacture of H2 SO4.
- in the preparation of aqua regia.
Q23. What are nitrides and azides?
The binary compounds of nitrogen with electro positive elements or with the elements which are less electronegative than nitrogen are called nitrides. While the salts of hydrazoic acid are called azides. Thus, Na3N Ag3N etc. are the examples of nitrides, while NaN3 AgN3, etc are the examples of azides.
Q24. Why does nitrogen differ from the other members of this group.
This is because of the following inherent properties of nitrogen: (a) small size (b) higher electronegativity, and (c) non-availability of d-orbitals. The main points of difference are:
- Nitrogen is a gas while other elements are solids.
- Nitrogen atom cannot expand its octet, while the other members of this group can do so.
- Nitrogen shows a large number of oxidation states, while the other elements do not show such a variety of oxidation states.
- Nitrogen is chemically inert due to high dissociation energy of N ≡ N bond. However, other elements of the group are quite reactive.
Q25. What are the natural methods of nitrogen fixation?
In nature nitrogen is fixed by the following methods.
By lightning discharges.
The nitrogen and oxygen present in air combine together to form nitric oxide under the influence of lightning discharges. Nitric oxide is oxidized by excess of oxygen present in the atmosphere to form nitrogen peroxide which further combines with water to form nitric acid.
By symbiotic bacteria.
The atmospheric nitrogen is being constantly transferred to the soil through the agency of certain bacteria called symbiotic bacteria. These grow in small nodules in roots of plants belonging to the family Leguminaceae (Pea, gram etc.).
Q26. Why nitrous oxide is called laughing gas?
When this oxide is inhaled in small quantities, it produces hysterical laughter and for this reason this oxide is called laughing gas.
Q27. What is microcosmic salt?
Sodium ammonium hydrogen phosphate [Na (NH4 ) HPO4, 4H2 O] is called microcosmic salt since it is present in the urine of the “microcosm” i.e., man.
Q28. What is phossy jaws?
White phosphorus has garlic odour and highly poisonous. It is used in match factories. Workers in match factories suffer from a disease called phossy jaws in which bones of jaw and teeth decay. This disease is due to white phosphorus
Q29. What is transition temperature?
It is the temperature at which one allotropic form of a substance changes into other. It has a fixed value for each pair of allotropes.
Q30. What do you know about diamond?
Diamond is the hardest substance known. Among various forms of carbon, diamond is the purest and densest. It has the highest refractive index, 2. 45. This property is responsible for its value as gems.
Q31. What do you know about Koh-i-Noor?
Koh-i-Noor (mountain of light) is a famous diamond of large size which had the original weight of 186 carats (1 gram = 5 carats) but had to be out down to 106 carats later on.