ICSE Class 10 Chemistry: Periodic Properties and Their Variations
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Master the Modern Periodic Table: 50+ Key ICSE Class 10 Questions Answered!
Welcome, ICSE Class 10 champions! The Modern Periodic Table is not just a chart of elements; it's the roadmap to understanding the entire world of chemistry. Mastering its trends and properties is crucial for acing your board exams.
This comprehensive guide breaks down over 50 of the most important questions on the Periodic Table, complete with clear, simple explanations. Whether you're revising periodic properties or tackling tricky concepts like ionization potential, we've got you covered. Let's get started!
🧪 Why Periodic Properties Matter in ICSE Class 10
The Periodic Table chapter is one of the most scoring parts of ICSE Class 10 Chemistry. Every year, questions on periodic trends appear in board exams. By mastering this topic, you can secure easy marks.
This guide will explain the most important periodic properties, their trends, and give you exam-style solved questions.
Down a Group: Increases (extra shell added).
Exam Question:
👉 Arrange F, Cl, Br, I in increasing atomic size.
✅ Answer: F < Cl < Br < I.
Part 1: The Basics of the Periodic Table (Periods & Groups)
First, let's build a strong foundation. These questions cover the fundamental structure of the periodic table.
1. Q: State the number of elements in Period 1 of the Periodic Table.
A: There are 2 elements in Period 1.
Explanation: Period 1 corresponds to the filling of the first energy level (K-shell), which can hold a maximum of 2 electrons.
2. Q: Name the elements in Period 1.
A: Hydrogen and Helium.
Explanation: These two elements complete the K-shell. Hydrogen has 1 electron, while Helium has 2, making its shell complete.
3. Q: State the number of elements in Period 2 of the Periodic Table.
A: There are 8 elements in Period 2.
Explanation: Period 2 involves filling the second shell (L-shell), which can accommodate a maximum of 8 electrons, hence there are 8 elements.
4. Q: State the number of elements in Period 3 of the Periodic Table.
A: There are 8 elements in Period 3.
Explanation: Period 3 involves filling the M-shell up to 8 electrons for stability, so it also contains 8 elements.
5. Q: What is the term for a horizontal row in the Periodic Table?
A: A Period.
Explanation: Elements in the same period have the same number of electron shells. There are 7 periods in the Modern Periodic Table.
6. Q: What is meant by a Group in the Periodic Table?
A: A vertical column of elements.
Explanation: Elements within the same group have the same number of valence (outermost) electrons, giving them similar chemical properties.
7. Q: The properties of the elements are a periodic function of their __________.
A: Atomic number.
Explanation: This is the Modern Periodic Law. It states that the chemical and physical properties of elements are a periodic function of their atomic number, not their atomic mass.
8. Q: Which number is used to arrange elements in the Periodic Table?
A: Atomic number.
Explanation: The Modern Periodic Table, proposed by Henry Moseley, arranges elements in increasing order of their atomic number.
9. Q: The similarities in the properties of a group of elements are due to the same __________.
A: Number of outer electrons (valence electrons).
Explanation: Since chemical reactions primarily involve the loss, gain, or sharing of valence electrons, elements with the same number of them behave similarly.
10. Q: What happens to the number of valence electrons on moving down a group?
A: It remains the same.
Explanation: This is the defining feature of a group. For example, all elements in Group 1 have 1 valence electron.
11. Q: What atomic property remains the same across a period?
A: Number of shells.
Explanation: As you move across a period, electrons are added to the same outermost shell. For instance, all Period 2 elements have 2 electron shells.
12. Q: To which period do Li, Be, B, C, N, O, F, Ne belong?
A: Period 2.
Explanation: All these elements have their electrons filling up the second energy shell (L-shell).
Part 2: Atomic Size and Its Variations
Atomic size is a fundamental property that influences all other trends. Let's see how it varies.
13. Q: What happens to the atomic size of elements on moving from left to right in a period?
A: The atomic size decreases.
Explanation: Across a period, the nuclear charge (number of protons) increases, but the number of shells stays the same. The stronger pull from the nucleus draws the electrons closer, reducing the atomic radius.
14. Q: What atomic property increases across a period, causing atomic size to decrease?
A: Nuclear charge.
Explanation: With each step across a period, a proton is added to the nucleus, increasing its positive charge and its pull on the electrons.
15. Q: Within a group, where is the element with the largest atomic size found?
A: At the bottom.
Explanation: As you go down a group, a new electron shell is added for each element. This increase in the number of shells outweighs the increase in nuclear charge, causing the atomic size to increase significantly.
Part 3: Metallic vs. Non-Metallic Character
The periodic table clearly divides metals from non-metals. Here’s how their character changes.
16. Q: If an element has one electron in its outermost shell, is it metallic or non-metallic?
A: It is metallic.
Explanation: Elements with 1, 2, or 3 valence electrons (like Na, K, Mg) tend to lose them easily to form positive ions (cations). This tendency to lose electrons is the key characteristic of metals.
17. Q: If an element is in Group 17 (or 7A), is it metallic or non-metallic in character?
A: It is non-metallic.
Explanation: Group 17 elements (halogens) have 7 valence electrons. They have a strong tendency to gain one electron to achieve a stable octet, which is a characteristic of non-metals.
18. Q: When moving across a period, which character increases – metallic or non-metallic?
A: Non-metallic character increases.
Explanation: As you move from left to right, the tendency to lose electrons decreases, while the tendency to gain electrons increases. Therefore, elements become less metallic and more non-metallic.
19. Q: The elements at the bottom of a group show __________ metallic character than the element at the top.
A: More metallic character.
Explanation: Down a group, the atomic size increases. The outermost electron is further from the nucleus and less tightly held, making it easier to lose. This increases the metallic character.
20. Q: Within a group, where is the element with the greatest metallic character found?
A: At the bottom.
Explanation: Due to the large atomic size and low ionization energy at the bottom of a group, these elements can lose electrons most easily, making them the most metallic.
21. Q: In the group B, Al, Ga, In, Tl, which shows the most metallic character?
A: Thallium (Tl).
Explanation: This group is Group 13. As metallic character increases down the group, Thallium (Tl), being at the bottom, is the most metallic.
22. Q: Based on metallic character trend in Period 2, which elements are metals?
A: Lithium (Li) and Beryllium (Be).
Explanation: Metallic character is highest on the left side of a period and decreases to the right. Li (Group 1) and Be (Group 2) are metals, while the rest are metalloids or non-metals.
Part 4: Key Periodic Properties Explained
These four properties—Ionization Potential, Electron Affinity, and Electronegativity—are exam favorites!
23. Q: State whether ionization potential increases or decreases on going down a group.
A: It decreases.
Explanation: Ionization potential is the energy needed to remove an electron. Down a group, the atomic size increases, weakening the nucleus's pull on the outermost electron, making it easier to remove.
24. Q: How does ionization potential of an element above chlorine compare with chlorine?
A: It is higher.
Explanation: The element above Chlorine (Cl) is Fluorine (F). Fluorine is smaller than chlorine, so its nucleus holds its electrons more tightly. This means more energy is needed to remove an electron from Fluorine.
25. Q: What happens to ionization potential across a period?
A: It increases.
Explanation: Across a period, atoms become smaller and the nuclear charge increases. This stronger attraction makes it more difficult (requires more energy) to remove an electron.
26. Q: What is the energy released when an atom accepts an electron called?
A: Electron Affinity.
Explanation: This property measures the change in energy when an electron is added to a neutral atom in its gaseous state to form a negative ion.
27. Q: What happens to electron affinity across a period (Groups 1 to 17)?
A: It generally increases.
Explanation: As atoms become smaller and the nuclear charge increases across a period, their attraction for an incoming electron becomes stronger, leading to a greater release of energy.
28. Q: What happens to electronegativity across a period?
A: It increases.
Explanation: Electronegativity is the ability of an atom to attract shared electrons in a bond. The increasing nuclear charge across a period enhances this ability.
29. Q: In the group B, Al, Ga, In, Tl, which has the highest electronegativity?
A: Boron (B).
Explanation: Electronegativity decreases as you go down a group because the larger atomic size reduces the nucleus's ability to attract the bonding electrons.
30. Q: How does the electronegativity of an element below sodium compare with sodium?
A: It is lower.
Explanation: The element below Sodium (Na) is Potassium (K). Since electronegativity decreases down a group, Potassium has a lower value than Sodium.
31. Q: Arrange Fluorine, Beryllium, and Nitrogen in increasing order of electronegativity.
A: Be < N < F.
Explanation: All three are in Period 2. As electronegativity increases from left to right across a period, Beryllium (Group 2) is the least electronegative, followed by Nitrogen (Group 15), and then Fluorine (Group 17) is the most electronegative.
Part 5: Applying Your Knowledge (Valency, Bonding & Formulas)
Let's apply these concepts to predict formulas, bonding, and electron configurations.
32. Q: What is the common feature of the electronic configuration of the elements at the end of Period 2 and 3?
A: A full outermost energy level (8 valence electrons, or an octet).
Explanation: The noble gases at the end of each period (like Neon in Period 2 and Argon in Period 3) have a stable octet configuration, which makes them chemically inert.
33. Q: Which feature of atomic structure explains the similarities in chemical properties of Group 17?
A: The same number of outer electrons.
Explanation: All halogens (Group 17) have 7 valence electrons. This common electronic structure dictates their similar chemical behavior, such as their tendency to gain one electron.
34. Q: How many electrons are present in the valence shell of the element with atomic number 18? A: 8 electrons.
Explanation: The element with Z=18 is Argon. Its electronic configuration is 2, 8, 8. The outermost shell (valence shell) has 8 electrons.
35. Q: What is the electronic configuration of the element in Period 3 which gains one electron to form an anion?
A: The element is Chlorine, and its configuration is 2, 8, 7.
Explanation: An element in Period 3 that gains one electron is in Group 17. This is Chlorine (Z=17), which has 7 valence electrons and readily gains one to complete its octet, forming the Cl⁻ anion.
36. Q: What is the electronic configuration of Aluminium (Al)?
A: 2, 8, 3.
Explanation: Aluminium has an atomic number (Z) of 13. Its 13 electrons are arranged in shells as 2 in the K-shell, 8 in the L-shell, and 3 in the M-shell.
37. Q: If Aluminium (2,8,3) has 3 valence electrons, how many does Thallium have?
A: 3 valence electrons.
Explanation: Both Aluminium and Thallium are in Group 13. All elements in the same group have the same number of valence electrons.
38. Q: Write the formula of the sulphate of the element with atomic number 13.
A: Al₂(SO₄)₃.
Explanation: The element with atomic number 13 is Aluminium (Al). It has 3 valence electrons and forms an Al³⁺ ion. The sulphate ion is SO₄²⁻. To balance the charges, you need two Al³⁺ ions (total charge +6) and three SO₄²⁻ ions (total charge -6), giving the formula Al₂(SO₄)₃.
39. Q: Atomic number of Boron is 5. Write the formula of the compound it forms with Chlorine.
A: BCl₃.
Explanation: Boron (Z=5) has a configuration of 2, 3. It has a valency of 3. Chlorine has a valency of 1. By criss-crossing the valencies, the formula becomes BCl₃ (Boron trichloride).
40. Q: What type of bonding is present in the oxide of the element with atomic number 1? A: Covalent bonding. Explanation: The element with atomic number 1 is Hydrogen. Its oxide is water (H₂O). Both Hydrogen and Oxygen are non-metals, so they share electrons to form covalent bonds.
Part 6: Quick-Fire Round - Identify and Arrange!
Test your knowledge with these rapid-fire questions about specific elements and their properties.
41. Q: One element is missing in the sequence Li, Be, B, C, O, F, Ne. Which one?
A: Nitrogen (N), which comes between Carbon (C) and Oxygen (O).
Explanation: The sequence lists elements of Period 2 in order of atomic number. Carbon (Z=6) is followed by Nitrogen (Z=7) and then Oxygen (Z=8).
42. Q: Which element among Li, Be, B, C, N, O, F, Ne belongs to the halogens?
A: Fluorine (F).
Explanation: Group 17 elements are known as halogens. Fluorine is the first element of this group.
43. Q: Which element is the first member of the group including Al, Ga, In, Tl?
A: Boron (B).
Explanation: This is Group 13 of the periodic table, which starts with Boron.
45-50. Review Questions:
- Q: What happens to non-metallic character across a period? (A: It increases)
- Q: What happens to electronegativity down a group? (A: It decreases)
- Q: What happens to atomic size down a group? (A: It increases)
- Q: How many elements are in Period 2? (A: 8 elements)
- Q: What is the valency of the element with configuration 2, 8, 7? (A: 1, as it needs to gain one electron)
- Q: What is the basis for the modern periodic table? (A: Atomic Number)
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