Answer:
2.10x10⁻⁹ moles of Si, 143.7 moles of CCl₄, 3.49x10²⁴ atoms
Explanation:
These is the relation:
NA (6.02x10²³) ⇒ 1 mol of particles (it can be, atoms or molecules)
This are the rule of three:
NA of atoms occupies 1 mol of Si
1.27x10¹⁵ atoms will occupy (1.27x10¹⁵ .1 ) / NA = 2.10x10⁻⁹ moles of Si
NA of molecules are contained in 1 mol of CCl₄
8.65x10²⁵ molecules are contained in (8.65x10²⁵ .1)/ NA = 143.7 moles
1 mol of Ca has NA atoms
5.80 moles of Ca will have (5.80 . NA) = 3.49x10²⁴
The element group which is least likely to form ions is 4A group
<u><em>explanation</em></u>
Element of group 4A has 4 valence electrons. for example Carbon which has [He] 2S2 2P2 electron configuration has 4 valence electrons.
Since 4A elements has 4 valence electrons , it means that their valence shell is half filled which is relatively stable. <em>For this reason 4A element readily form ions.</em>
Answer:
18
Explanation:
the numbers at the top tell you
B moisture evaporating from an ocean
Answer: The average atomic mass of oxygen is 15.999 amu
Explanation:
Mass of isotope O-16 = 15.995 amu
% abundance of isotope O-16= 99.759 % = 
Mass of isotope O-17 = 16.995 amu
% abundance of isotope O-17 = 0.037% = 
Mass of isotope O-18 = 17.999 amu
% abundance of isotope O-18 = 0.204% = 
Formula used for average atomic mass of an element :

![A=\sum[(15.995\times 0.99759)+(16.995\times 0.00037)+(17.999 \times 0.00204)]](https://tex.z-dn.net/?f=A%3D%5Csum%5B%2815.995%5Ctimes%200.99759%29%2B%2816.995%5Ctimes%200.00037%29%2B%2817.999%20%5Ctimes%200.00204%29%5D)

Thus the average atomic mass of oxygen is 15.999 amu