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

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.