Question 1

Which element from following has positive electron gain enthalpy?

Accepted Answer

Electron gain enthalpy is the enthalpy change when an electron is added to a neutral gaseous atom. Halogens such as Chlorine, Bromine, and Iodine have a strong tendency to accept an electron to achieve a stable noble gas configuration, resulting in highly negative electron gain enthalpies. Noble gases like Xenon have a completely filled and stable valence shell (ns^2 np^6). Adding an electron requires energy to place it in a higher energy principal quantum shell, overcoming interelectronic repul

Question 2

Which of the following elements belongs to group 2 and sixth period of periodic table?

Accepted Answer

Group 2 elements are alkaline earth metals: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). The periods corresponding to these elements are: Period 2: Beryllium Period 3: Magnesium Period 4: Calcium Period 5: Strontium Period 6: Barium Period 7: Radium Therefore, the element belonging to group 2 and the sixth period is Barium. Answer: Barium

Question 3

Identify the most electronegative element by the following.

Accepted Answer

Electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself. According to the Pauling scale, the electronegativity values of the given elements are: Fluorine: 4.0 Oxygen: 3.5 Nitrogen: 3.0 Chlorine: 3.0 Fluorine has the highest electronegativity among all elements in the periodic table. Answer: Fluorine

Question 4

Identify increasing order of acidity for following diprotic acids in aqueous solutions.

Accepted Answer

The given compounds are hydrides of Group 16 elements. As we move down the group from Sulphur (S) to Tellurium (Te), the atomic size of the central atom increases. This leads to an increase in the H-E bond length (where E is S, Se, Te) and a corresponding decrease in the bond dissociation enthalpy. Consequently, the H-E bond becomes weaker, making the release of an H ^ + ion easier. Therefore, the acidic strength increases down the group. The increasing order of acidity is H _2 S Answer: H _2 S

Question 5

Identify the group of periodic table that contains element Astatine.

Accepted Answer

Astatine (At) is a chemical element with atomic number 85. It belongs to the halogen family, which includes Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (At), and Tennessine (Ts). The halogen family is located in Group 17 of the modern periodic table. Answer: 17

Question 6

What happens to the size of atoms in p-block elements when we move from left to right in the same period?

Accepted Answer

As we move from left to right across a period, the atomic number increases, meaning the number of protons in the nucleus increases. The additional electrons are added to the same principal shell, so the shielding effect remains almost constant. This results in an increase in the effective nuclear charge (Z_ eff ), which pulls the valence electrons closer to the nucleus. Consequently, the atomic size decreases from left to right in the same period. Answer: Size decreases

Question 7

Which group elements have the smallest atomic radii in their respective periods?

Accepted Answer

In a given period, the atomic radius decreases from left to right as the effective nuclear charge increases. This trend continues up to group 17 (halogens). For group 18 (noble gases), the atomic radius is expressed as van der Waals radius since they do not form covalent bonds under normal conditions. Since van der Waals radii are always larger than covalent radii, group 18 elements have larger radii than group 17 elements. Thus, group 17 elements possess the smallest atomic radii in their respe

Question 8

Which of the following compounds is most acidic in nature?

Accepted Answer

The given compounds are hydrides of Group 16 elements. As we move down the group from oxygen to tellurium, the atomic size of the central atom increases. Due to the increase in atomic size, the bond length of the H-E bond (where E is O , S , Se , Te ) increases, which leads to a decrease in the bond dissociation enthalpy. A lower bond dissociation enthalpy means the H-E bond can be broken more easily to release an H ^+ ion. Therefore, the acidic character increases down the group. The order of a

Question 9

Which of the following hydrides of Group 16 elements has highest reducing property?

Accepted Answer

The reducing property of Group 16 hydrides depends on the ease with which they can release hydrogen atoms. As we move down the group from oxygen to tellurium, the atomic size of the central atom increases. This leads to an increase in the E- H bond length (E = O, S, Se, Te ) and a corresponding decrease in the bond dissociation enthalpy. Due to the lowest bond dissociation enthalpy among the given options, H _2 Te releases hydrogen most easily. Therefore, the reducing property increases in the o

Classification of Elements and Periodicity in Properties — Previous Year Questions & Solutions