Why there is jump of 14 atomic numbers from La (57) to Hf (72)?

There is continuous decrease in atomic radii from Lanthanum (La) to Lutetium (Lu). Give reason. What are its consequences ?

Why do transition elements show variable oxidation states ? Name the element showing maximum number of oxidation states among the first series of transition metals from Sc (Z = 21) to Zn (Z= 30).

A radioactive nucleus A undergoes a series of decays according to the following scheme: A oversetalphararrA_1oversetbetararrA_2 oversetalphararrA_3oversetgammararrA_4 The mass number and atomic number of A are 180 and 72 respectively. What are these number for A_4 .

The question refers to the elements of the periotic table with atomic number from 3 to 18. Which of these: is/are noble gas? is a halogen? is an alkali metal? Write the electron configuration of G. If A combines with F, what would be the formula of resulting compound?

In Geiger-Marsden experiment,a 5 MeV alpha -particle is scattered through 180^@ from the gold foil.If the atomic number of gold is 79 ,find the distance of closet appraoch to the gold nucleus.

What is the potential gradient ( in Vm^-1 ) at a distance o 10^-12 m from the centre fo the platinum nucleus? What is the potential gradient at the surface of nucleus? Atomic number of platinum is 78 and the radius of platinum nucleus may be taken as 5 xx 10^-15 m.

An analysis of the rock shows that the relative number of Sr^(87) and Rb^(87) (t_(1//2)=4.7 xx10^(10) year) atoms is 0.05 . What is the age of the rock? Assume all the Sr^(87) have been formed from Rb^(87) only a) 7.26 xx10^(9) year b) 1.43 xx 10^(9) year c) 3.28 xx 10^(9) year d) 4.32 xx10^(8) year

In the transition series starting from Lanthanum (atom no =57), the next element hafmnium (atom no =72) why so observe this jump in atomic number ?