The atomic number of an element is 12. based on its electron arrangement, which of the following explains its correct position in the periodic table?
a)group 3, because it has two electrons in the 3p orbital.
b)group 2, because it has two electrons in the 3p orbital.
c)group 3, because its last electron is in the 3p orbital.
d)group 2, because its last electron is in the 2p orbital.

Group 2, because it has two electrons in the 3s orbital.

Explanation:

Electronic configuration represents the total number of electrons that a neutral element contains.Thus for element with atomic number 12 contains 12 electrons.

The electrons are filled according to Afbau's rule in order of increasing energies and thus the electronic configuration is :

As the element belongs to s-block, as last electron enters s orbital,  its group number = Number of valence electrons (or outermost shell electrons), which is 2.

Thus group number is 2.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

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