Answer:
All the members of a group of elements have the same number of valence electrons and similar chemical properties.
Explanation:
The vertical columns on the periodic table are called groups or families because of their similar chemical behavior.
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Answer : The final concentration of
is, 2.9 M
Explanation :
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = 
t = time passed by the sample = 3.5 min
a = initial concentration of the reactant = 3.0 M
a - x = concentration left after decay process = ?
Now put all the given values in above equation, we get


Thus, the final concentration of
is, 2.9 M
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They are nitrogen, oxygen, hydrogen