When an electron occupies an orbital of an atom singly, rather than an electron pair such electron is said to be an unpaired electron. Each atomic orbital of an atom specified by quantum numbers can contain a maximum of two electrons having opposite spins, electron pair.
The numbers of unpaired electrons are determined by the electronic configuration of an atom. The electronic configuration of calcium, 
is:
or ![[Ar]4s^{2}](https://tex.z-dn.net/?f=%5BAr%5D4s%5E%7B2%7D)
Since, from the electronic configuration it is clear that the number of electrons in valence orbital that is 
is 2 that means the electrons are paired up in the valence orbital so, there are no unpaired electrons present in .
Hence, the number of unpaired electrons in is 0.
Differential weathering or erosion
Answer:
Option c → 8:1
Explanation:
This is the reaction:
C₅H₁₂ + 8O₂ → 10CO₂ + 6H₂O
1 mol of pentane needs 8 moles of oxygen to be combusted and this combustion produces 10 mol of carbon dioxide and 6 moles of water.
To determine the ratio, look the stoichiometry.
For every 8 moles of oxygen, I need 1 mole of pentane gas.
Non metallic elements pull electrons from metallic elements so effectively during a reaction because they have a tendency to gain electrons and tend to be small in size.
<span>Non metallic elements have higher electronegativities than metals. The atoms of nonmetals tend to gain electrons in order to acquire a noble gas electron configuration. This gives them a net negative electric charge. </span>
