Answer is: a. Rubidium (Rb) is more reactive than strontium (Sr) because strontium atoms must lose more electrons.
The ionization energy (Ei) is the minimum amount of energy required to remove the valence electron, when element lose electrons, oxidation number of element grows (oxidation process).
Alkaline metals (group 1), in this example rubidium, have lowest ionizations energy and easy remove valence electrons (one electron), they are most reactive metals.
Earth alkaline metals (group 2), in this example strontium, have higher ionization energy than alkaline metals, because they have two valence electrons, they are less reactive.
Rubidium electron configuration: ₃₇Rb 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s¹; one valence electron is 5s¹ orbital.
Strontium electron configuration: ₃₈Sr 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s²; two valence electrons is 5s² orbital.
The study strategy Lauren is using in spreading her study sessions over a period of time is pacing, which helps the student develop a schedule focused on their own study pace.
<h3>Pacing Study Sessions</h3>
This study strategy of distributing the study into short sessions rather than studying the entire content through one long session is more effective in retaining content and learning.
What happens is that Lauren is using mass repetition processing, which can be compared to a longitudinal wave in physics, with spaces in between, concentrating the initial review close to the proof to ensure retention and avoid forgetting.
Through pacing, Lauren achieves greater motivation to carry out her studies in a concentrated and focused way, helping her to retain and preserve knowledge.
The correct answer is:
Find out more information about pacing here:
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Answer : The concentration of 
ion is 0.0375 M.
Explanation :
The balanced equilibrium reaction will be:
The expression for solubility constant for this reaction will be,
![K_{sp}=[Pb^{2+}][Cl^-]^2](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BPb%5E%7B2%2B%7D%5D%5BCl%5E-%5D%5E2)
Now put all the given values in this expression, we get:
![2.40\times 10^{-4}=[Pb^{2+}]\times (0.0800)^2](https://tex.z-dn.net/?f=2.40%5Ctimes%2010%5E%7B-4%7D%3D%5BPb%5E%7B2%2B%7D%5D%5Ctimes%20%280.0800%29%5E2)
![[Pb^{2+}]=0.0375M](https://tex.z-dn.net/?f=%5BPb%5E%7B2%2B%7D%5D%3D0.0375M)
Therefore, the concentration of ion is 0.0375 M.
The curved top of a liquid is the meniscus
