The answer is D, Magnesium.
For an anion or cation(negatively or positively charged ion) to replace a similarly-charged ion, it needs to be more active. This means that only a cation that is above Zinc on the reactivity scale can replace Zinc.
Since Aluminum was displaced in the reaction, that means the unknown metal is more reactive.
This means that our options are:
Lithium, Potassium, Calcium, Sodium, and Magnesium.
But because the metal did not displace the Sodium, it must be less reactive than it.
This gives us a new list of metals that are less-reactive than Sodium:
Magnesium, Aluminum, Zinc, Iron, Nickel, etc.
The only metal on both lists is Magnesium, and that means that your answer is D, Magnesium.
Answer:is it c 0.80-0.34
hope its right
my bsf told me the answer
Explanation:
Answer:
( B) They all have their valence electrons in the same type of subshell.
Explanation:
With each period, a new shell is added to the atom.
Further, the groups are classified based on the type of subshell the last electron enters and number of valence electrons.
For all elements of same group, the last electron enters the same type of subshell.
Say, for group 1, last electron enters s orbital and they have 1 valence elctron.
for group 17, last electron enters p orbital and they have 7 valence electrons.
(A) and (D) are wrong because, energy level of the valence electrons is determined by the principle quantum number n and l and not by the type of subshell(only l) they enter.
(C) if the valence electron enters p orbital, then the elements will be placed in the p- block.
Answer:- 9.4 minutes.
Solution:- Radioactive decay obeys first order reaction kinetics and the equation used to solve this type of problems is:
where, k is decay constant and t is the time. 
is the initial amount of the radioactive substance and N is the remaining amount.
Since the value of decay constant is not given, so we need to calculate it first from given half life by using the formula:
where 
stands for half life.
Given half life is 3.0 minutes.
So, 
Let's plug in the values in the first order reaction equation and solve it for t.
It could also be written as:
k = 9.4 min
So, the radioactive substance would take 9.4 minutes to decay from 40.0 grams to 4.5 grams.
