Question

19) How many significant figures are in 1009.630 mL? A) 3 B) 4 C) 5 D) 6 E) 7 F) 8 20) How many different values of my are possible in the 4f sublevel? A) 1 B) 3 C) 5 D) 7 E) 9 F) 11

Answer 1

19)

The significant figure in a decimal number are count by taking all the numbers befor and after the decimal , because all the number positions are needed for precision . Now . for the number 1009.630 , 4 numbers places are there before decimal and 3 numbers are there after decimal ( you may think the last 0 is useless after decimal , but actually , it is not ) . So , significant figure = (4+3) = 7

So , correct answer is option E ) 7 .

20)

For 4f sublevel , the suborbit is f .

The azimuthal quantum no . for suborbit f is (l=3) .  

The number of magnetic quantum no. is given by the equation -

$\dpi{120} \bg_white m_{l}=(2\times l+1)$

Thus , for l=3 ,

$\dpi{120} \bg_white m_{l}=(2\times 3+1)$

$\dpi{120} \bg_white \therefore m_{l}=7$

And the magnetic quantum no. s are(+l to -l ) , that is -(+3,+2,+1,0,-1,-2,-3) .

Thus there are 7 different types of m_l possible .

Correct answer is option D) 7 .