Silver (atomic weight =108gmol−1 has density of 10.5 gcm−3 The number of silver atoms on a surface of area 10−12m2 can be expressed in scientific notation as y×10x  The value of x is

Volume of one mole of silver atoms 10810.5cm3/ mole volume of one silver atom =10810.5×16.022×1023cm3So 43πR3=10810.5×16.022×1023=1.708×10−23R3=0.407×10−23cm3,R3=0.407×10−29m3Area of each silver atomπR2=π×0.407×10−29m32/3so, number of silver atoms in given area.=10−120.407×10−29m32/3=108(π×2)=1.6×107=y×10×x=7.