To remove magnesium oxide layer from the ribbon which may prevent or slow down the burning of magnesium ribbon.
1 valence electron in alkali metals.
<u>Answer:</u> The correct answer is Option A.
<u>Explanation:</u>
Electronegativity is defined as the tendency of an atom to attract the shared pair of electrons towards itself whenever a bond is formed.
This property increases as we move from left to right across a period because the number of charge on the nucleus gets increased and electrons are attracted more towards the nucleus.
This property decreases as we move from top to bottom in a group because the electrons get add up in the new shells which make them further away from the nucleus.
Thus, the correct answer is Option A.
<span>19.992*0.9048+20.993*0.0027+21.991+0.0925 = </span><span> 20.1797 amu (C)</span>