180 



Atomic 

 Number. 

 3. 

 4. 

 6. 

 7. 



11. 

 12. 

 13. 

 14. 

 16. 

 17. 

 19. 

 20. 

 22. 

 24. 



25. 



26. 

 27. 

 28. 

 29. 

 30. 

 33. 

 34. 

 35. 

 37. 

 38. 

 47. 

 48. 

 50. 

 51. 

 52. 

 53. 

 55. 

 56. 

 81. 

 82. 

 83. 



Prof. W. L. Bragg on the 



Atomic Atomic 

 Element. Diameter, in A. Radius, in A. 



Lithium 300 1-50 



Beryllium 2-30 1-15 



Carbon L54 0'77 



Nitrogen.... 1*30 0'65 



Oxygen 1*30 0'65 



Fluorine 1*35 67 



Sodium 3'55 177 



Magnesium 2 85 142 



Aluminium 2*70 T35 



Silicon 2-35 1-17 



Sulphur 2-05 1-02 



Chlorine 2*10 1*05 



Potassium 4*15 2'07 



Calcium 3 ; 40 L70 



Titanium 280 1'40 



Chromium 2"80 T40 



("electronegative") 2*35 117 



Manganese 295 1*47 



("electronegative") 2 - 35 1*17 



Iron 2-80 1-40 



Cobalt 2-75 1'37 



Nickel 2-70 1-35 



Copper 2 - 75 1*37 



Zinc 265 1-32 



Arsenic 2'52 1-26 



Selenium 2'35 117 



Bromine 2'38 1*19 



Rubidium 4-50 225 



Strontium 3*90 195 



Silver 3-55 177 



Cadmium 3'20 L60 



Tin 280 1-40 



Antimony 2'80 L40 



Tellurium 2'65 T33 



Iodine 280 L40 



Caesium 475 2*37 



Barium 4"20 210 



Thallium 4*50 225 



Lead 380 190 



Bismuth 2'96 T48 



Atomic 



Compound. centres. 



Element Li. 



LiF. Li,F. 



LiCl. Li, CI. 



LiBr. Li,Br. 



Lil. Li,I. 



Sum of radii, Observed Difference, 



o o o 



in A. Distance, in A. in A. 



3-00 

 l-504-0-67=2-17 

 1-50 + 1-05 = 2-55 

 l-50+M9=2-69 

 l-50+l-40=2-90 



303 



2-05 

 2-57 

 2-79 

 315 



+ 0-03 

 -0-12 

 +0-02 

 + 0-10 

 +025 



Element Be. 



BeO. 



Be,0. 



2-30 2-52 +022 



* Assumiug close packing. 



1-15 +0-65 =1-80 1-78 -0*02 1 



t Assuming ZnO structure. 



