* :

( ....... ) . .

* :

( ) 10-8 . 10-13

* :

( )

:

. ( a.m.u )

. . = 67 * 10-24

:

( ) . ( ) 12 .

(Z=1 A=1)

:

9.11 * 10-28 1840 .

* :

( orbits ) ( K ) ( ) . ( L ) ( M ) 18 32 . :

() = 2 2

: ( = 1 ) = 2 * 21 = 2

( = 2 ) = 2 * 22 = 8

* (A) (Z):

. = 2 + 2 = 4

: = = a.m.u () a.m.u = 4 a.m.u .

: (Z) = 2