Question

The following questions refers to the periodic table:
 $ (I) $ Name the second last element of the period $ 3 $
 $ (II) $ How many elements in the second period?
 $ (III) $ Name the element which has the highest electron affinity?
 $ (IV) $ Name the element which has highest electronegativity.

Answer 1

Hint: Electronegativity is the tendency of the atoms of an element to attract electrons when they are chemically combined with another element. The value of electronegativity generally lies between $ 0.7 $ to $ 3.98 $ . On the other hand, Electron affinity is the attraction of a neutral atom for an additional electron. Electron affinity is known to be fixed since the electron releases almost a similar amount of energy when it is added to an atom.

Complete answer:
 $ (I) $ The second last element of the periodic table is chlorine. Chlorine is a chemical element with the symbol $ Cl $ and atomic number $ 17 $ . The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidizing agent among the elements.
 $ (II) $ The second period contains the elements lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the second shell, more specifically its $ 2s $ and $ 2p $ subshells.
 $ (III) $ Chlorine has the highest electron affinity. Fluorine is a small atom with a small amount of space available in its $ 2p $ orbital. Because of this, any new electron trying to attach to fluorine experiences lower affinity from the electrons already living in the elements $ 2p $ orbitals. Since chlorine outermost orbital is a $ 3p $ orbital, there is more space, and the electrons in this orbital are inclined to share this space with extra electron.
 $ (IV) $ Fluorine has the highest electronegativity and cesium the lowest. This indicates that fluorine has a high tendency to gain electrons from other elements with lower electronegativities.

Note:
There are two factors that can affect electron affinity. These are atomic size and nuclear charge. The smaller the atom is, the closer the outermost shell is therefore, there is a stronger attraction between the nucleus and the incoming electron. That means the electron affinity is higher for smaller atoms.