Question

Which is/are false about electronegativity order of the following elements?
a.) P > Si
b.) C > N
c.) C > Br
d.) Se > Ca

Answer 1

Hint: When we move left to right in the periodic table, the size of the atom decreases while the nuclear charge increases. So, the value of electronegativity increases. But when we move top to bottom, the size of the atom increases more than the increase in nuclear charge due to addition of new orbits. As a result, the value of electronegativity decreases here.

Complete step by step answer:

First, we will understand what is electronegativity and its natural trend on moving left to right and top to bottom in the periodic table. Then, we will see the options.

Electronegativity can be defined as the tendency of an atom to attract the shared bond pair towards itself. There are various factors which govern this property.

On moving left to right in the periodic table, the size of the atom decreases while the nuclear charge increases. As a result, the value of electronegativity increases.

On moving top to bottom, the size of the atom increases. There is an increase in nuclear charge but due to the addition of new orbital, the size overpowers. As a result, the value of electronegativity decreases.

Now, let’s see options one by one.

So, the option a.) says that P has more electronegativity than Silicon. This statement is true because while moving left to right in the third period, the Silicon comes first and then the Phosphorus. So, phosphorus is more electronegative than Silicon.

Now, moving to option b.). It says that Carbon is more electronegative than Nitrogen. This statement is false because Carbon and Nitrogen both belong to the same period and carbon comes before nitrogen. Thus, nitrogen has more electronegativity than carbon.

The option c.) says that Carbon is more electronegative than Bromine. This statement is false because Bromine belongs to the halogen family which requires only one electron to complete its octet. Thus, bromine is much more electronegative than carbon.

Now, the last option d.) which says that Selenium is more electronegative than Calcium. This statement is true because while moving left to right in the fourth period, the Calcium comes before Selenium. Thus, Selenium is more electronegative than Calcium.

So, the option a.) and option d.) are true while the options b.) and c.) are false.

Thus, the correct answer is option b.) and option c.).


Note:

On moving left to right in the periodic table, there is one unit increase in nuclear charge while the addition of electrons takes place in the same orbital. As a result, the forces of attraction increase and the size decreases. Due to small size, the nucleus can easily attract the shared pair also towards itself and thus electronegativity increases.

While on moving down a group, each time with an increase in one unit nuclear charge, the addition of electrons takes place in the new orbital. So, the distance of valence electrons from the nucleus decreases and as a result, the electronegativity decreases.