Question 1: Briefly explain the main principle behind Mendeleev's periodic table arrangement.

Answer: Mendeleev arranged elements in order of increasing atomic mass, grouping elements with similar properties into columns, and left gaps for undiscovered elements.

Question 2: What was one significant prediction made by Mendeleev using his periodic table?

Answer: He predicted the existence and properties of elements like gallium and germanium before they were discovered.

Question 3: Multiple Choice: Which of the following was a key feature of Mendeleev's periodic table? A) Elements were arranged strictly by atomic number. B) Elements with similar properties were grouped into columns. C) The table included only known elements at the time. D) Atomic masses were ignored in the arrangement.

Answer:

Question 4: Fill in the blank: Mendeleev left __________ in his periodic table to account for elements that had not yet been discovered.

Answer: gaps

Question 5: Explain why Mendeleev's periodic table was considered innovative despite some inaccuracies in atomic masses.

Answer: Mendeleev's periodic table was innovative because it grouped elements by similar properties and predicted the existence of undiscovered elements, which demonstrated its usefulness and predictive power despite inaccuracies in atomic mass ordering.

Question 6: Describe one reason why Mendeleev's periodic table was later replaced by the modern periodic table.

Answer: It was replaced because atomic number, not atomic mass, was found to be the fundamental property determining element placement.

Question 7: What safety precautions should be considered when working with chemicals related to the discovery of elements, according to theoretical experiments?

Answer: Wearing protective gloves, goggles, working in a well-ventilated area, and following proper handling procedures for hazardous substances.

Question 8: Calculate the difference in atomic mass between two elements if element A has an atomic mass of 23.0 u and element B has an atomic mass of 39.9 u. Show your calculation.

Answer: Difference = 39.9 u - 23.0 u = 16.9 u

Question 9: In the context of Mendeleev's periodic table, explain how the gaps helped in discovering new elements.

Answer: The gaps indicated positions where elements with specific properties and atomic masses were missing, guiding scientists to search for and discover new elements fitting those criteria.

Question 10: Provide a real-world example of how Mendeleev's periodic table influenced modern chemistry or industry.

Answer: It laid the foundation for the modern periodic table, helping chemists understand element properties, leading to the development of new materials and technologies such as semiconductors and pharmaceuticals.