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  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (BeF4)2

                      SECTION A CONCEPTUAL AND APPLICATION TYPE QUESTIONS  1 Is the force acting between two point charges q1 and q2 kept at some distance apart in air attractive or repulsive when i) q1 q2 > 0 ii) q1 q2 < 0 ? 1 (2007)  2 If the distance between two equal point charges is doubled and their individual charges are also doubled ,what would happen to the force between them ? 1(2014)  3 Do the electrostatic field lines form closed loops? 1(2014)  4 A hollow metal sphere of radius 5cm is charged such that the potential on its is 10V. What is the electric field at the center of the sphere? 1(2011)  5 What is meant by the statement that   “the electric field of a point charge has spherical symmetry whereas electric field due to an electric dipole is cylindrically symmetrical’’ ? 1(1996)  6 Why is it difficult to perform electrostatic experiments on a humid day? 1  7 The distance of the field point on the equatorial plane of a small electric dipole , is halved. By wha

Ques 1. Mention the condition when an object is in motion (a) can be considered point object (b) can not be considered point object.  Ans . An object can be considered as a point object if (a) its size is negligible in comparison to the distance travelled by object (b) it's size is not negligible in comparison to the distance travelled by object. Ques 2 . Can Earth be regarded as a point object when it is describing its really journey around the sun? Ans.  Yes, because the diameter of earth is very small as compared to the radius of the orbital path of earth around the sun.   Ques 3. Can the speed of a body be negative?   Ans . No, because the speed of an object is the distance travelled by the by object in unit time and distance can never be negative. Ques 4. which speed is measured by the speedometer of your scooter?  Ans . The Speedometer measure the instantaneous speed of the scooter at a given instant of time. Ques 5.What does the slope of position time 

                  QUANTUM NUMBERS  Orbitals represent regions in the space around the nucleus where the probability of finding the electron is maximum. A large number of electron orbitals are possible in atom. These can be distinguished by their size, shape and orientation of the orbitals. To describe each electron in an atom in different orbitals, we need a set of three numbers known as quantum numbers. These are designated as n, l and m. In addition to these three numbers another quantum number is also needed which specifies the spin of the electron. These four numbers are called quantum numbers. These are discussed below: 1. Principal quantum number (n) :  This quantum number determines the main energy shell or level in which the electron is present. It is denoted by n. It can have whole number values starting from 1 such as n = 1, 2, 3, 4 ... This quantum number also identifies as shell. The shell with n 1 is called the first shell. The shell with n 2 is called the second shell and

Ques 1 : Which of the statements about the reaction below are incorrect?              2 P b O  +  C → 2 P b + CO (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced. (i) (a) and (b) (i i) (a) and (c) (i i i) (a), (b) and (c) (i v) all Ans 1: (i)(a) and (b) Ques 2: The above reaction is an example of a:              Fe 2 O 3 +2 Al →Al 2 O 3  + 2 Fe (a) combination reaction. (b) double displacement reaction. (c) decomposition reaction. (d) displacement reaction. Ans 2: (d) The given reaction is an example of a displacement reaction. Ques 3: What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. (a) Hydrogen gas and iron chloride are produced. (b) Chlorine gas and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced. Ans 3: (a) Hydrogen gas and iron chloride are produced. The reaction is as  follows