3. look at the positions of calcium, beryllium, and magnesium on the periodic table. based on their locations, predict how many valence electrons these elements have and predict what the reactivity of these elements will generally be.

Explanation:

It is known that beryllium, calcium and magnesium are all group 2 elements.

Atomic number of Be is 4, magnesium has 12 and calcium has atomic number 20.

So, they contain 2 valence electrons and in order to attain stability they readily lose their valence electrons.

As a result, they tend to form an ion with +2 charge.

Since, it is easy to lose two electrons to attain stability hence, elements of group 2 are very reactive in nature.

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.