Atomic Structure MCQ's PDF

1. Who proposed the idea that atoms are solid spheres? a) J.J. Thomson b) John Dalton c) Ernest Rutherford d) Niels Bohr Answer: b) John Dalton *Explanation: John Dalton proposed that atoms are solid spheres and that the atoms in any given element were identical and could not be divided.* 2. Which...

1. Who proposed the idea that atoms are solid spheres? a) J.J. Thomson b) John Dalton c) Ernest Rutherford d) Niels Bohr Answer: b) John Dalton *Explanation: John Dalton proposed that atoms are solid spheres and that the atoms in any given element were identical and could not be divided.* 2. Which model of the atom includes a ball of positive charge with electrons embedded in it? a) Solid Sphere Model b) Plum Pudding Model c) Nuclear Model d) Planetary Model Answer: b) Plum Pudding Model *Explanation: J.J. Thomson discovered electrons and proposed the Plum Pudding Model, where atoms are made up of a ball of positive charge with negative electrons embedded in it.* 3. What did Rutherford's gold foil experiment demonstrate? a) Atoms are indivisible. b) Atoms have electrons embedded in positively charged pudding. c) Most of the atom consists of empty space with a central nucleus. d) Electrons exist in fixed orbits around the nucleus. Answer: c) Most of the atom consists of empty space with a central nucleus. *Explanation: Ernest Rutherford's experiment showed that most of an atom was empty space, with the positive charge centered in a nucleus.* 4. Who discovered the neutron? a) John Dalton b) J.J. Thomson c) Ernest Rutherford d) James Chadwick Answer: d) James Chadwick *Explanation: James Chadwick discovered the neutron in 1932. This added to the understanding of the atom introduced by earlier models.* 5. What is the charge of a proton? a) -1 b) 0 c) +1 d) +2 Answer: c) +1 *Explanation: Protons have a relative charge of +1.* 6. Which particle has a very small relative mass and a -1 charge? a) Proton b) Neutron c) Electron d) Positron Answer: c) Electron *Explanation: Electrons have a very small relative mass and a charge of -1.* 7. What is the relationship between the number of protons and electrons in a neutral atom? a) Protons = Electrons b) Protons > Electrons c) Protons < Electrons d) Unrelated Answer: a) Protons = Electrons *Explanation: In a neutral atom, the number of protons equals the number of electrons, balancing the charges.* 8. What term describes atoms of the same element with different numbers of neutrons? a) Isotopes b) Ions c) Electrons d) Isomers Answer: a) Isotopes *Explanation: Isotopes are atoms with the same number of protons but different numbers of neutrons.* 9. If a neutral atom has 6 protons and 8 neutrons, what is its atomic number? a) 6 b) 8 c) 12 d) 14 Answer: a) 6 *Explanation: The atomic number is equal to the number of protons, which is 6 in this case.* 10. What is the mass number of an atom with 12 protons and 13 neutrons? a) 12 b) 13 c) 25 d) 26 Answer: c) 25 *Explanation: The mass number is the sum of protons and neutrons; hence, 12 + 13 = 25.* 11. What factor predominantly determines the chemical properties of an element? a) Number of protons b) Number of neutrons c) Number of electrons d) Mass number Answer: c) Number of electrons *Explanation: The chemical properties of an element are determined by its electronic configuration.* 12. What is the definition of "relative atomic mass"? a) The mass of the most abundant isotope b) The average mass of all isotopes of an element considering their abundances c) The sum of masses of protons and neutrons d) The difference in mass between the nucleus and electron cloud Answer: b) The average mass of all isotopes of an element considering their abundances *Explanation: The relative atomic mass takes into account both the mass of each isotope and their relative abundances.* 13. When calculating relative atomic mass (Ar) from percentages, what do you divide the sum of isotope masses times their abundances by? a) 50 b) 100 c) Total number of isotopes d) Atomic number Answer: b) 100 *Explanation: The relative atomic mass calculation involves dividing the sum by 100, as the abundances are given in percentages.* 17. Which scientist proposed that electrons exist in fixed orbits (energy levels) around the nucleus? a) John Dalton b) J.J. Thomson c) Ernest Rutherford d) Niels Bohr Answer: d) Niels Bohr *Explanation: Niels Bohr proposed that electrons exist in orbits around the nucleus at fixed distances, known as energy levels.* 18. The term "fundamental particles" refers to which particles in an atom? a) Protons and isotopes b) Electrons and neutrons c) Protons, neutrons, and electrons d) Neutrons and isotopes Answer: c) Protons, neutrons, and electrons *Explanation: Fundamental particles refer to protons, neutrons, and electrons which make up an atom.* 19. Which isotope calculation process involves summing the mass of isotopes multiplied by their abundance and dividing by 100? a) Determining atomic number b) Calculating Relative Atomic Mass (Ar) c) Finding mass number d) Spectral analysis Answer: b) Calculating Relative Atomic Mass (Ar) *Explanation: Relative Atomic Mass (Ar) calculation involves summing the products of isotope masses and their abundances, then dividing by 100.* 20. What did Rutherford's model suggest about the structure of the atom? a) Atoms are solid and indivisible. b) Atoms consist of a dense nucleus surrounded by electrons. c) Atoms are positively charged spheres with embedded electrons. d) Electrons exist in uniform probability clouds. Answer: b) Atoms consist of a dense nucleus surrounded by electrons *Explanation: Rutherford's nuclear model suggested a dense, positively charged nucleus with electrons orbiting it in empty space.* 21. If you know the mass number and the atomic number of an isotope, how can you find the number of neutrons? a) Subtract the atomic number from the mass number b) Add the atomic number to the mass number c) Multiply the atomic number by the mass number d) Divide the mass number by the atomic number Answer: a) Subtract the atomic number from the mass number *Explanation: The number of neutrons is found by subtracting the atomic number (number of protons) from the mass number (total protons + neutrons).* 22. Which concept explains the relative abundance of isotopes in nature? a) Mass number b) Atomic number c) Relative Atomic Mass (Ar) d) Isotopic distribution Answer: c) Relative Atomic Mass (Ar) *Explanation: Relative Atomic Mass takes into account the mass and relative abundance of different isotopes.* 24. Who discovered that electrons are embedded in a sphere of positive charge (Plum Pudding Model)? a) John Dalton b) Ernest Rutherford c) J.J. Thomson d) Niels Bohr Answer: c) J.J. Thomson *Explanation: J.J. Thomson discovered electrons and proposed the Plum Pudding Model with electrons embedded in a positive sphere.* 26. How many neutrons are present in the isotope 35-Cl? a) 17 b) 18 c) 35 d) 52 Answer: b) 18 *Explanation: The number of neutrons is mass number minus atomic number: 35 - 17 = 18.* 27. If an atom has 8 protons, 10 neutrons, and 8 electrons, which element is it and what is its mass number? a) Oxygen, mass number 16 b) Neon, mass number 18 c) Oxygen, mass number 18 d) Carbon, mass number 12 Answer: c) Oxygen, mass number 18 *Explanation: Oxygen has 8 protons, and the mass number is protons plus neutrons; thus, mass number is 8 + 10 = 18.* 29. Who proposed that atoms are mostly empty space, with electrons orbiting a dense nucleus? a) Ernest Rutherford b) John Dalton c) J.J. Thomson d) Niels Bohr Answer: a) Ernest Rutherford *Explanation: Ernest Rutherford's gold foil experiment led to the nuclear model, proposing that atoms are mostly empty space surrounding a dense nucleus.* 30. Which of the following best describes an isotope? a) Atoms with different numbers of protons but the same number of neutrons b) Atoms with the same number of protons but different numbers of neutrons c) Atoms with the same number of neutrons but different numbers of electrons d) Molecules formed from the same element Answer: b) Atoms with the same number of protons but different numbers of neutrons *Explanation: Isotopes are variants of the same element with the same number of protons but different numbers of neutrons, leading to different atomic masses.*