Worksheet on Periodic Classification of Elements

Solved Questions on Periodic Classification of Elements

1. Which of the following elements belong to the I. same group and II. same period?

a) I: P, S; II: Q, R
b) I: P, Q, R; II: R, S
c) I: Q, S; II: P, R
d) I: P, S; II: P, Q, and R

Answer: d) The elements P and S belong to the same group because they have the same number of valence electrons, which is 1. They are both in Group 1, known as the alkali metals. The elements P, Q, and R belong to the same period because they have the same number of electron shells (energy levels) in their atomic structure. In this case, they are all in the fourth period of the periodic table. Element S is in a different period as it has more electron shells.

2. Arrange the following elements in order of increasing electronegativity:

a) Cl < S < P < Al
b) S < P < Cl < Al
c) P < S < Al < Cl
d) Al < P < S < Cl

Answer: d) Cl (Chlorine) is the most electronegative element among the options, as it is a halogen and belongs to Group 17 (Group VIIA) of the periodic table. Halogens are known for their high electronegativity.

S (Sulphur) is next in electronegativity as it is a non-metal and is to the right of P (Phosphorus) and Al (Aluminum) in the periodic table.
P (Phosphorus) is a non-metal but has a slightly lower electronegativity compared to sulphur.
Al (Aluminum) is a metal and has the lowest electronegativity among these elements.

3. Which of the following statements is correct regarding the trends when going down a group in the modern periodic table?

I. The atomic number decreases.
II. The number of valence shells remains the same.
III. The atomic radius generally increases.
IV. Metallic character increases.

a) I, IV
b) III, IV
c) II, III, IV
d) Only III

Answer: b) The atomic radius generally increases when going down a group. This is because each new element in the group has an additional energy level (valence shell), leading to a larger atomic size. Metallic character increases when going down a group. Hence, these statements are correct.
The atomic number does not decrease when going down a group; it increases. Each new element in a group has a higher atomic number than the one above it. Also, the number of valence shells increases when going down a group. Each new element in the group has an additional energy level (valence shell), so the number of valence shells increases. So, these statements are incorrect.

4. You are given two elements, X and Y, from the same period of the periodic table. Element X is on the left side of the period, and element Y is on the right side. Which element is more likely to form a cation?

a) Element X
b) Element Y
c) Both X and Y
d) Neither X nor Y

Answer: a) Element X, which is on the left side of the period in the periodic table, is more likely to form a cation. Elements on the left side of the periodic table, especially metals, tend to lose electrons to achieve a stable electron configuration. When they lose electrons, they form positively charged ions called cations. This behaviour is characteristic of elements in Groups 1 and 2 and some transition metals.

Element Y, being on the right side of the period, is more likely to form anions (negatively charged ions) by gaining electrons to achieve a stable electron configuration. This is typical of nonmetals on the right side of the periodic table.

5. In a laboratory experiment, you observe that when element X reacts with water, it produces an alkaline solution and hydrogen gas is released. Which group in the periodic table is element X most likely to belong to?

a) Alkali metals
b) Halogens
c) Noble gases
d) Alkaline earth metals

Answer: a) Element X is most likely to belong to the alkali metals group in the periodic table. Alkali metals are known for their strong reactivity with water, producing alkaline solutions and releasing hydrogen gas when they react with it. This behaviour is a characteristic feature of alkali metals like lithium (Li), sodium (Na), potassium (K), and others in Group 1 of the periodic table.

FAQs

1. Who developed the first Periodic Table?

Dmitri Mendeleev created the first Periodic Table in 1869. With precise property predictions, he organised elements according to their atomic masses, leaving spaces for as-yet-undiscovered elements.

2. How is the modern Periodic Table arranged?

The modern Periodic Table is arranged based on the increasing order of atomic numbers. Elements with similar chemical properties are grouped into columns called groups, while elements with the same number of electron shells are placed in the same row or period.

3. How are metals, nonmetals, and metalloids distributed in the Periodic Table?

In the Periodic Table, metals are typically located on the left, non-metals on the right, and metalloids along the zigzag line. The different physical and chemical characteristics of these elements are reflected in their distribution.

4. How does the Periodic Table help in predicting chemical reactions?

The tendency of elements to receive, lose, or share electrons is illustrated by the Periodic Table, which helps anticipate chemical reactions. Because they have the same valence electron configuration, elements in the same group frequently show comparable reactions.

5. What is the difference between metals, nonmetals, and metalloids?

Non-metals are weak conductors compared to metals, while metalloids combine the characteristics of both. These groups are made up of elements according to the Periodic Table, which makes it easier to comprehend their chemical and physical properties.