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Writer's pictureVikas Yadav

Important Questions from Periodic Table | Class XI | CBSE and ISC Board

Here are the answers to the 50 important questions related to the periodic table:

 

1. What is the periodic table? 

   The periodic table is a tabular arrangement of all known chemical elements, organized based on their atomic number, electron configurations, and recurring chemical properties.

 

2. Who is credited with the creation of the modern periodic table? 

   Dmitri Mendeleev, a Russian chemist, is credited with creating the first widely recognized periodic table in 1869.

 

3. How are elements arranged in the periodic table? 

   Elements are arranged in order of increasing atomic number (number of protons) from left to right and top to bottom.

 

4. What is a period in the periodic table? 

   A period is a horizontal row in the periodic table. There are 7 periods in the modern periodic table, and each period represents a new principal energy level.

 

5. What is a group in the periodic table? 

   A group is a vertical column in the periodic table. There are 18 groups, and elements within the same group share similar chemical properties due to having the same number of valence electrons.

 

6. How many periods are there in the modern periodic table? 

   There are 7 periods in the modern periodic table.

 

7. How many groups are there in the modern periodic table? 

   There are 18 groups in the modern periodic table.

 

8. What are the main types of elements found in the periodic table? 

   The main types of elements are metals, non-metals, and metalloids.

 

9. What is the significance of the periodic law? 

   The periodic law states that the properties of elements are periodic functions of their atomic numbers. This means that elements with similar properties recur at regular intervals when arranged by increasing atomic number.

 

10. How are metals, non-metals, and metalloids distributed in the periodic table? 

    Metals are found on the left side and in the middle of the periodic table, non-metals are on the right side, and metalloids are located along the zigzag line that separates metals and non-metals.

 

### Properties of Elements in the Periodic Table:

 

11. What are the alkali metals? Name the elements that belong to this group. 

    Alkali metals are highly reactive metals found in Group 1 of the periodic table. They include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

 

12. What are the alkaline earth metals? Name the elements that belong to this group. 

    Alkaline earth metals are reactive metals found in Group 2 of the periodic table. They include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

 

13. What are the halogens? Name the elements that belong to this group. 

    Halogens are highly reactive non-metals found in Group 17 of the periodic table. They include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

 

14. What are the noble gases? Name the elements that belong to this group. 

    Noble gases are inert gases found in Group 18 of the periodic table. They include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

 

15. What is the general electronic configuration of alkali metals? 

    The general electronic configuration of alkali metals is ns1, where (n) represents the period number.

 

16. What is the general electronic configuration of noble gases? 

    The general electronic configuration of noble gases is ns2 np^6, except for helium, which has 1s2.

 

17. How does the atomic size change across a period? 

    Atomic size decreases across a period from left to right due to increasing nuclear charge, which pulls the electrons closer to the nucleus.

 

18. How does the atomic size change down a group? 

    Atomic size increases down a group because each successive element has an additional electron shell, making the atom larger.

 

19. What is ionization energy, and how does it vary in the periodic table? 

    Ionization energy is the energy required to remove an electron from a gaseous atom. It increases across a period (left to right) and decreases down a group.

 

20. What is electronegativity, and how does it change across a period and down a group? 

    Electronegativity is the ability of an atom to attract electrons in a chemical bond. It increases across a period and decreases down a group.

 

### Trends in the Periodic Table:

 

21. What is electron affinity, and how does it change across a period? 

    Electron affinity is the energy change that occurs when an electron is added to a gaseous atom. It generally becomes more negative (increases) across a period.

 

22. Explain the trend of metallic character across a period. 

    Metallic character decreases across a period from left to right as elements become less likely to lose electrons.

 

23. Explain the trend of non-metallic character down a group. 

    Non-metallic character decreases down a group as elements become more likely to lose electrons (increased metallic character).

 

24. What is the trend of density across periods and groups in the periodic table? 

    Density generally increases across a period and varies down a group. Heavier elements tend to have higher densities.

 

25. How does the reactivity of metals change in the periodic table? 

    The reactivity of metals decreases across a period and increases down a group.

 

26. How does the reactivity of non-metals change in the periodic table? 

    The reactivity of non-metals increases across a period and decreases down a group.

 

27. Why do elements in the same group have similar chemical properties? 

    Elements in the same group have the same number of valence electrons, leading to similar chemical behaviour.

 

28. How does melting and boiling points vary across periods and down groups? 

    Melting and boiling points generally increase towards the middle of a period (peaking at transition metals) and vary irregularly down a group.

 

29. What is the trend in the size of cations and anions across a period? 

    Cation size decreases across a period due to increased nuclear charge, while anion size also decreases but less drastically.

 

30. How does the shielding effect change down a group? 

    The shielding effect increases down a group as additional electron shells are added, increasing electron-electron repulsion.

 

### Special Groups and Series:

 

31. What are transition elements? Provide examples. 

    Transition elements are metals found in Groups 3-12, characterized by partially filled d-orbitals. Examples include iron (Fe), copper (Cu), and gold (Au).

 

32. What are lanthanides, and where are they located in the periodic table? 

    Lanthanides are a series of 15 elements from lanthanum (La) to lutetium (Lu), found in the f-block of Period 6.

 

33. What are actinides, and where are they located in the periodic table? 

    Actinides are a series of 15 elements from actinium (Ac) to lawrencium (Lr), found in the f-block of Period 7. They are all radioactive.

 

34. What are representative elements? Provide examples. 

    Representative elements are elements in the s-block and p-block (Groups 1, 2, 13-18). Examples include carbon (C), oxygen (O), and sodium (Na).

 

35. What are inner transition elements? 

    Inner transition elements are elements found in the f-block, which includes the lanthanides and actinides.

 

36. What is the significance of the d-block elements in the periodic table? 

    D-block elements, known as transition metals, are significant due to their ability to form coloured compounds, variable oxidation states, and their role as catalysts.

 

37. How are the s-block and p-block elements different in terms of properties? 

    S-block elements are highly reactive metals, while p-block elements include both metals and non-metals with varying reactivities. P-block also contains metalloids and noble gases.

 

38. What are f-block elements, and why are they placed separately? 

    F-block elements include lanthanides and actinides, known for their complex electron configurations. They are placed separately to keep the periodic table compact and to emphasize their unique properties.

 

39. What are noble gases, and why are they called inert gases? 

    Noble gases are elements in Group 18 that are chemically inert due to their full valence electron shell, making them very stable.

 

40. How are transition metals different from alkali and alkaline earth metals? 

    Transition metals have partially filled d-orbitals, exhibit multiple oxidation states, and often form colored compounds, unlike alkali and alkaline earth metals, which have s-orbital valence electrons and are highly reactive.

 

### Applications and Importance:

 

41. Why is the periodic table important in chemistry? 

    The periodic table organizes elements systematically, allowing chemists to predict properties, behaviors, and reactions of elements, making it a vital tool for understanding chemical science.

 

42. How does the periodic table help predict chemical behavior? 

 By knowing an element’s position, chemists can predict its reactivity, bonding tendencies, and interaction with other elements based on periodic trends.

 

43. How are the properties of an element determined by its position in the periodic table? 

    An element’s properties are determined by its atomic number, electron configuration, and its location within specific periods and groups, reflecting trends in reactivity and other chemical properties.

 

44. Why are some elements placed in the same group? 

    Elements in the same group have similar valence electron configurations, resulting in similar chemical properties and reactivity.

 

45. What are isotopes, and how are they represented in the periodic table? 

    Isotopes are atoms of the same element with different numbers of neutrons. They are represented by the element symbol with different mass numbers.

 

46. How does the periodic table assist in understanding periodic trends? 

    The table’s arrangement highlights periodic trends in atomic size, ionization energy, electron affinity, electronegativity, and metallic character, which helps in predicting element properties.

 

47. Why is hydrogen placed separately in the periodic table? 

    Hydrogen is placed separately because it has unique properties, resembling both alkali metals (one valence electron) and halogens (nonmetal characteristics), and it forms compounds with most elements.

 

48. How does the periodic table help in the study of chemical reactions? 

    The table allows chemists to predict which elements will react with each other, the products of reactions, and the type of bonds that will form based on trends and group properties.

 

49. What is the significance of the modern periodic table compared to Mendeleev's periodic table? 

    The modern periodic table is organized by increasing atomic number rather than atomic mass, correcting anomalies, and better reflecting periodic trends. It also includes more elements discovered after Mendeleev’s time.

 

50. How has the periodic table evolved over time, and what are the recent additions? 

    The periodic table has evolved with the discovery of new elements and better understanding of atomic structure. Recent additions include elements up to atomic number 118, such as Oganesson (Og).

 

These questions and answers provide a comprehensive understanding of the periodic table, its structure, properties, and significance in the study of chemistry.

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