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Aadya Singh 3 years, 10 months ago
agar achha nhi soch or bol skte.. To bura bhi mat bolo....
aur na hi hum 2020 me roye the.. na royenge 2021 me ?
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Yogita Ingle 3 years, 10 months ago
“The physical and chemical properties of elements are a periodic function of their atomic weights”
This means that physical and chemical properties of elements depends on their atomic weight such that on arranging elements in increasing order of atomic weight, elements with similar properties are repeated after regular intervals of increasing atomic weight.
Posted by Aadya Singh 3 years, 10 months ago
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Divyansh Rai 3 years, 10 months ago
Yogita Ingle 3 years, 10 months ago
The formal charge over an atom of a polyatomic molecule or ion is the difference between the valence electron of that atom in the elemental state and the number of electrons assigned to that atom in Lewis structure.
Mathematically, it can be expressed by following formula:
F.C. = [Total no. of valence e– in free state] – [total no. of e– assigned in Lewis structure] F.C. = [Total no. of valence e– in free state] – [total no. of non-bonding pair e– (lone pair)] – 1/2 [total no. of bonding e–]
The factor of ½ is attached to the no. of bonding e– because bonding e– is shared between two atoms.
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Yogita Ingle 3 years, 10 months ago
What is mass percentage composition of each element present in ehanol
Answer:
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Arpit Pandey 3 years, 10 months ago
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Yogita Ingle 3 years, 10 months ago
Common physical features of alkali metals:
(1) They are soft and can be easily cut.
(2) They have silvery white appearance. They are light coloured.
(3) Due to large atomic size, they have low density. On moving down the group the density increases with exception of K which has lower density than Na.
(4) Due to weak metallic bonding, alkali metals have low melting and boiling points.
(5) They provide characterisitc colour to flames.
(6) They show photoelectric effect. On irradiation with lightCs and K lose electrons.
Common chemical features of alkali metals:
Due to low ionization enthalpy, akali metals have high reactivity.
On moving down the group, the reactivity increases.
(1) On reaction with water, oxides and hydroxides are formed.
On moving down the group, the reaction becomes more and more vigorous.
(2) On reaction with water, hydroxide and hydrogen are formed.
2M+2H2O→2MOH+H2
(3) On reaction with hydrogen, hydrides are formed.
2M+H2→MH
(4) They directly combine with halogens to form ionic halides. Li is an exception.
2M+Cl2→2MCl,(M=Li,K,Rb,Cs)
(5) They are strong reducing agents. On moving down the group, the reducing power increases with exception of Li. Due to high hydration energy, Li is the strongest reducing agent among alkali metals.
(6) They dissolve in liquid ammonia. The solution is deep blue in colour due to presence of ammoniated electrons.
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Yogita Ingle 3 years, 10 months ago
Pyrolysis is defined as the conversion of a compound into smaller fragments in the absence of air through the application of heat. It is different from combustion. It happens in the absence of air and hence oxidation of compounds does not take place. Generally, pyrolysis of alkanes is also named as cracking.
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Yogita Ingle 3 years, 10 months ago
Magnesium nitrate crystallizes with six molecules of water while barium nitrate crystallizes as the anhydrous salt. This again shows that the tendency to form hydrates decreases with increasing size and decreasing hydration enthalpy down the group.
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Yogita Ingle 3 years, 10 months ago
Germanium was called eka-silicon in Mendeleef's time.
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?Ritesh Gupta? 3 years, 10 months ago
1Thank You