The elements of same group are placed in same group as they have similar properties. So Calcium is the element which resembles Mangesium.
Calcium and Magnesium both are alkaline earth metals.
They have similar properties as they have similar outer or valence shell electronic configuration
The general electronic configuration of alkaline earht metal is ns2
The electronic configuration of Mg [atomic number 12] and Ca [atomic number 20] are
![[Ne]3s^{2}](https://tex.z-dn.net/?f=%5BNe%5D3s%5E%7B2%7D)
and ![[Ar]4s^{2}](https://tex.z-dn.net/?f=%5BAr%5D4s%5E%7B2%7D)
respectively.
Answer:
B. 
Explanation:
The unit for rate is M/s while the unit for each molecule should be M. You can find the unit for k by putting the units for rate and the molecules into the equation
rate= k{X][Y]
M/s= k * 
* 
k= (M/s) / (
)
k=
You can also use this predetermined formula to solve this problem faster: k= 
Where n is the number of molecule. There are 3 molecule(2X and 1Y) so n=3, so
k=
k= 
= 
=
Explanation:
3CaBr2 + 2K3N → 6KBr + Ca3N2
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