Question 1: Describe Dmitri Mendeleev's main contribution to the development of the Periodic Table.

Answer: Dmitri Mendeleev created the first periodic table arranged by increasing atomic weight, leaving gaps for undiscovered elements and predicting their properties.

Question 2: Explain the significance of Mendeleev leaving gaps in his periodic table.

Answer: The gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict their properties accurately.

Question 3: What was the main principle behind Mendeleev's arrangement of elements?

Answer: Elements were arranged by increasing atomic weight and similar chemical properties were grouped together.

Question 4: Identify one limitation of Mendeleev’s periodic table based on his method of arrangement.

Answer: It sometimes grouped elements incorrectly because atomic weights did not always increase steadily, leading to some elements being misplaced.

Question 5: How did Mendeleev's periodic law differ from the modern periodic law?

Answer: Mendeleev's periodic law stated that properties of elements are a periodic function of their atomic weights, while modern law states properties are a function of atomic number.

Question 6: Calculate the number of protons in an atom of an element with atomic number 17.

Answer: 17

Question 7: Identify the element Mendeleev predicted, which has atomic weight around 68 and properties similar to aluminum.

Answer: Gallium

Question 8: A certain element has an atomic number of 16. Describe its likely properties based on Mendeleev's periodic table.

Answer: It is likely a non-metal, a gas at room temperature, with a strong smell, and forms compounds such as sulfur dioxide; it is also part of Group 16 (chalcogens).

Question 9: Explain one safety precaution that should be considered when handling elements similar to those in Mendeleev's table in a laboratory setting.

Answer: Always wear gloves and eye protection to prevent contact with potentially toxic or reactive elements.

Question 10: Describe how the discovery of protons influenced the development of the modern periodic table compared to Mendeleev’s arrangement.

Answer: The discovery of protons led to the understanding of atomic number as a more accurate basis for element classification, resulting in the modern periodic table arranged by increasing atomic number rather than atomic weight, fixing some placement issues in Mendeleev’s table.

Question 11: Identify a real-world application where the principles of Mendeleev's periodic table are used today.

Answer: The periodic table is used in the development of new materials, such as alloys and pharmaceuticals, by understanding element properties and relationships.