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The M shell can take a maximum of ____ electrons, but in Ca it has _____ electrons. [Atomic Number of Ca = 20]
18, 10
18, 8
8, 8
8, 10
18, 8
The maximum capacity of an electron shell is defined by the formula 2n squared, where n is the shell number. For the M shell (n=3), the capacity is 2 multiplied by 3 squared, which equals 18, but due to the octet rule and the Aufbau principle, the valence shell of Calcium (atomic number 20) only holds 8 electrons in its M shell to maintain stability.
The maximum capacity of an electron shell is defined by the formula 2n squared, where n is the shell number. For the M shell (n=3), the capacity is 2 multiplied by 3 squared, which equals 18, but due to the octet rule and the Aufbau principle, the valence shell of Calcium (atomic number 20) only holds 8 electrons in its M shell to maintain stability.
The electronic configuration of elements is the foundation of the Periodic Table developed by Dmitri Mendeleev, later refined into the Modern Periodic Law based on atomic numbers by Henry Moseley.
The K shell (n=1) holds 2 electrons, L shell (n=2) holds 8, M shell (n=3) holds 18, and N shell (n=4) holds 32.
Calcium (Ca, Z=20) has the electronic configuration 2, 8, 8, 2.
The rule that states shells are filled from lower to higher energy levels is known as the Aufbau Principle.
The M shell can theoretically hold 18 electrons, but elements following the octet rule prefer 8 electrons in their outermost occupied shell for chemical stability.
In Calcium, the 4th shell (N) begins filling before the M shell reaches its full capacity of 18, resulting in a 2, 8, 8, 2 configuration.
Option B is the correct answer because 18 is the mathematical maximum for the 3rd shell, while 8 is the actual occupancy in the Calcium atom.
B is correct тАФ The M shell has a mathematical capacity of 18 electrons based on 2n squared, but Calcium follows a 2, 8, 8, 2 configuration where the M shell holds 8.
When studying Chemistry for exams, always correlate electron configurations with group and period trends in the Periodic Table; Calcium (Group 2) belongs to the Alkaline Earth Metals.
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