3) B-X bond length in BX3 is shorter than theoretically expected . why ?
4) on moving down a group , size is expected to increase. then why radius of Ga < Al ?
Ans - this is due to filling of electrons in d-orbitals. in between Al and Ga there are 10 elements having electrons in d orbitals . as d orbitals are large in
5) why boron has a high m.p ???
6) B doesn't form ionic compounds . why ?
7) boron halides do not form dimers . why ?
8) trihalides of grp 13 fume in moist air . why ?
MX3 + 3H20 -> M(OH)3 + 3HX
9)TlCl is more stable than TlCl3 in aqueous solution .why ?
ans - due to inert pair effect
grp 13 ....continued
so the positively charged oxygen atom pulls sigma electrons of O-H bomd towards itself , releasing a proton .
it is becoz of the same reason that AlF3 has greater m.p than AlCl3
in Al2Cl6 each Al atom forms 3 covalent bonds with three chlorine atoms and one co -ordinate bond with the chlorine atom of another AlCl3 molecule.
2) greater polarity of Si - X bond ( X = H,C,N,O,F,Cl,I,Br )
3) availability of vacant d orbitals in Si
tin (IV) chloride is covalent in which weak intermolecular forces exists & makes it a liquid.
SnCl2 + H2O ----> Sn(OH)Cl + HCl
in presence of tin foil , HCl reacts to form SnCl2 again and thus helps in
Patterns in the Periodic Table
The periodic table is an arrangement of all the known elements in order of increasing atomic number. The reason why the elements are arranged as they are in the periodic table is to fit them all, with their widely diverse physical and chemical properties, into a logical pattern. If sodium is placed beneath lithium and not next door to fluorine, and potassium is placed beneath sodium to begin another row - and so on - it is found that the vertical lines of elements are chemically similar. These vertical lines are called GROUPS.
Horizontal lines of elements are called PERIODS. A set of D-BLOCK ELEMENTS, sometimes called the transition metals, occurs between Groups 2 and 13; these are also chemically similar to each other. Some Groups exhibit striking similarity between their elements, such as Group 1, and in other Groups the elements are less similar to each other, such as Group 4, but each Group has a common set of characteristics.
The periodic table is divided into BLOCKS.
The s-block elements have valence configuration s1 or s2.
The p-block elements have valence configuration s2p1 to s2p6.
The d-block elements have valence configurations in which d-subshells are being filled.
Hydrogen occupies a unique position at the top of the periodic table. It does not fit naturally into any Group.
All the members of a Group have the same valence configuration but different principal quantum numbers. The number of valence electrons equals the Group number. The period number equals the principal quantum number of the valence shell.
Chemically, elements in the same block exhibit the same general characteristics. This is most apparent for the s-block elements which are all metals with low electronegativity. The p-block elements are more varied with some metals such as aluminium on the left and non-metals on the right. Between them, indicating the gradual change in character going across the periodic table, are the metalloids (or semi-metals), which lie roughly in a diagonal line from silicon to tellurium. The d-block elements are often called the transition metals, but some of them, such as zinc, do not fit this description well. They are usually considered together as differences between Groups are much less apparent in this block.
Periodicity of some properties
Periodicity is the name given to regularly-occurring similarities in physical and chemical properties of the elements. Periodicity reflects the periodic repetition of similar electron configurations. Very many properties of the elements show periodicity. The most obvious of these is the continuing change from metal on the left to non-metal on the right.
This is reflected in the graph of melting points for the first 20 elements:
For each period the melting point rises from Group 1 to Group 14, then falls to the lowest value at Group 18. If the d-block elements are also included periodicity can be seen between rows of these elements, but as periodicity becomes less apparent with increasing atomic number this is less obvious than for the s- and p-block elements.
Variation of first ionisation energy with atomic number also shows striking periodicity. The relative position of each Group in relation to the others follows the same pattern in each period.
Periodicity is also seen for atomic radius and can be summarised by indicating the main trends:
Some chemical properties of the elements also follow trends and can be summarised in the same way. These include bonding, oxidising properties, acid-base properties of the oxides and electronegativity.
1. NCl3 can be hydrolysed .NF3 cant be hydrolysed . Why ?
Good work Bhuvana and rest. Lets keep this thread alive.
wow..........hats off to u all
Okay few more....
**Only in OF2(i.e.with fluorine).....O.S. of oxygen is +ve ;rest always -ve...
**[AlF6]- is formed but [BF6]- is not formed...
coz Boron does not hav d orbital 2 expand its octet...
**Same way PCl5 is formed but NCl5 isn't.....
**Distinctive properties in size...
Ga > Al & Tl > In (due 2 poor shieldind effect of d & f-orb. electorns..)
**Solution of borax in H2O is BASIC....why??
brks into.... NaOH + H3BO3 (As NaOH is strong electrolyte..it dissociates completely forming Na+ & OH- 2 give basic sol.n)
I didn't mean only "OF2"..... i meant 2 say compounds "like" OF2 where Oxygen is with fluorine...show Positive Oxidation states of oxygen....
With other elemnts O always has -ve Oxid. states.....as only Fluorine is more electro-ve than oxygen....
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