Estimate the average mass density of a sodium atom assuming its size to be about `2.5 overset@A`. (Use the known values of Avogadro’s number and the atomic mass of sodium). Compare it with the density of sodium in its crystalline phase : `970 kg m^-3`. Are the two densities of the same order of magnitude ? If so, why ?

Assume that each iron atom has a permanent magnetic moment equal to 2 Bohr magneton . The number density of atoms in iron is 8.52 xx 10^28 m^-3 . Find the maximum value of intensity of magnetisation.

Silver has atomic mass 108 a.m.u. and density 10.5 g cm^(-3) If the edge length of its unit cell is 409 pm, identify the type of unit cell. Also calculate the radius of an atom of silver.

The unit of length convenient on the nuclear scale is a fermi : 1 f = 10 ^-15 m . Nuclear sizes obey roughly the following empirical relation :- r=(r_0A)^(1/3) where ris the radius of the nucleus, Aits mass number, and r_o is a constant equal to about, 1.2 f. Show that the rule implies that nuclear mass density is nearly constant for different nuclei. Estimate the mass density of sodium nucleus. Compare it with the average mass density of a sodium atom obtained in Exercise. 2.27.

Sodium has a b.c.c. structure with nearest neighbour distance 365.9 pm, calculate its density. (Atomic mass of sodium = 23)

Assume that each iron atom has a permanent magnetic moment equal to 2 Bohr magneton . The number density of atoms in iron is 8.52 xx 10^28 m^-3 . Find the maximum value of magnetic induction in an iron bar.

Estimate the average drift speed of conductin electrons in a copper wire of cross sectional area 1.0xx10^(-7) m^2 carrying a current of 1.5 A. Assume that each copper atom contributes roughly one conduction electron. The density of copper is 9.0xx10^3 kgm^(-3) and its atomic mass is 63.5 u.

Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. Density of iron ·is 7.87 g cm^(-3) Use this information to calculate Avogadro's number. (Atomic mass of Fe= 56.0 u)

In a test experiment on a model aeroplane in a wind tunnel, the flow speeds on the upper and lower surfaces of the wing are 70 m s^-1 and 63 m s^-1 respectively. What is the lift on the wing if its area is 2.5 m^2 ? Take the density of air to be 1.3 kg m^-3

classically an electron can be in any orbit around nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? Thequestion had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as followswith the basic constants of nature e, me, c and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom (~ 10 m).- You will find that the length obtained above is many orders of magnitude smaller than the atomic dimensions. Further, it involves c. But energies of atoms are mostly in non-relativistic domain where c is not expected to play any role. This is what may have suggested Bohr to discard c and look for else h had already made its appearance elsewhere. Bohr lay in recognising that h, m_e , and e will yield the right atomic size. Construct a quantity with the dimension of length from h, me, and e and confirm that its numerical value has indeed the correct order of magnitude.