This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here are the answers to your chemistry exam questions: I. Write True if the statement is correct Or False if it is Incorrect (5 pts) 1. Isotopes of an element have Similar chemical properties. True 2. Mendeleev arranged the elements based on increasing order of atomic number. False (He arranged them by increasing atomic mass.) 3. Isobars are different atoms that have the same mass number. True 4. Atoms of the same element have the same number of neutrons. False (Isotopes of the same element have different numbers of neutrons.) 5. The mass of an electron is almost equal to the mass of a proton. False (The mass of an electron is much smaller than that of a proton.) II. Match column 'A' with column 'B' (5 Pts) 6. Dalton's Atomic Model → C. Billiard Model 7. J.J. Thomson Atomic Model → D. Plum-pudding Model 8. Rutherford's Atomic Model → B. Planetary Model 9. Bohr's Atomic Model → A. Orbit 10. Democritus Atomic Model → E. Solid sphere III. Choose The Correct Answer from the following alternatives (10 pts) 11. The Energy level in the third principal quantum number can accommodate C. 18 electrons. Explanation:* For a principal quantum number n, the maximum number of electrons is given by 2n^2. For n=3, the maximum is 2(3^2) = 2 × 9 = 18. 12. The mass of an atom is concentrated in B. Nucleus. Explanation:* The nucleus contains protons and neutrons, which account for almost all of an atom's mass. 13. Which fundamental particle does not present in the hydrogen atom? C. neutron. Explanation:* The most common isotope of hydrogen (^1_1H, protium) has one proton and one electron but no neutrons. 14. What is the average atomic mass of an element which Isotopic composition is 90% of ^20X and 10% of ^22X? D. 20.2. Calculation:* Average atomic mass = (0.90 × 20) + (0.10 × 22) = 18 + 2.2 = 20.2 15. Nucleus was discovered by B. Rutherford. Explanation:* Ernest Rutherford discovered the atomic nucleus through his gold foil experiment. 16. 1s^2 2s^2 2p^6 3s^2 3p^4 is an electronic configuration of D. _18Ar. Explanation:* The given electron configuration has 2+2+6+2+4 = 16 electrons, which corresponds to Sulfur (S). However, Sulfur is not an option. Assuming there is a typo in the question and the configuration should have been 1s^2 2s^2 2p^6 3s^2 3p^6 (18 electrons), then it would correspond to Argon (Ar). 17. How many Protons, electrons and neutrons are found in an atom of _35^80Br respectively? C. 35, 35, 45. Explanation:* Atomic number (Z) = 35, so there are 35 protons. For a neutral atom, the number of electrons equals the number of protons, so there are 35 electrons. Mass number (A) = 80. Number of neutrons = A - Z = 80 - 35 = 45. 18. An element has the valence shell electron configuration of 2s^2 2p^3 to which group and period does it belong? B. VA and 2. Explanation:* The highest principal quantum number is 2, so it belongs to Period 2. The total number of valence electrons is 2+3=5. Elements with 5 valence electrons are in Group VA (or Group 15). 19. The earliest of the attempts to classify elements was that of D. Dobereiner's triads. Explanation:* Dobereiner's triads (1829) were among the first attempts to group elements with similar properties. 20. How many elements