A substance has 13 protons, 14 neutrons, and 13 electrons. Which isotope is it? A) Al-13 B) Al-14 C) Al-27 D) Al-40 7. One isotope of oxygen has the atomic number 8 and the mass number 18. An atom of this isotope contains A) 8 neutrons B) 10 electrons C) 8 protons D) 18 electrons 8. Different isotopes of an element are atoms of that element which have A) The same atomic number and the same mass number B) The same atomic number and different mass number C) Different atomic number and the same mass number D) Different atomic number and different mass number 9. Which subatomic particle contributes least to the mass of the nucleus? A) Proton B) Neutron C) Electron 10. Which subatomic particle is not found in the nucleus of the atom? A) Proton B) Neutron C) Electron
The Correct Answer and Explanation is:
6. Which isotope is it?
The substance has 13 protons, 14 neutrons, and 13 electrons. The number of protons determines the atomic number of an element, which is 13, meaning this is an aluminum (Al) atom. The mass number is the sum of protons and neutrons, which is 13+14=2713 + 14 = 2713+14=27. This means the isotope is Al-27.
Answer: C) Al-27
7. An atom of this isotope contains:
The question describes an isotope of oxygen with the atomic number 8 and the mass number 18. The atomic number (8) tells you the number of protons in the atom, and for neutral atoms, the number of electrons equals the number of protons, which is 8. The mass number (18) is the total number of protons and neutrons. To find the number of neutrons, subtract the number of protons (8) from the mass number (18):
18−8=1018 – 8 = 1018−8=10 neutrons.
Answer: A) 8 neutrons
8. Different isotopes of an element are atoms of that element which have:
Isotopes are atoms of the same element with the same number of protons (which determines the atomic number) but a different number of neutrons. This results in a different mass number. Therefore, they have the same atomic number and different mass numbers.
Answer: B) The same atomic number and different mass number
9. Which subatomic particle contributes least to the mass of the nucleus?
The nucleus is made up of protons and neutrons. Protons and neutrons have roughly the same mass, which is significantly greater than the mass of electrons. Electrons are almost massless compared to protons and neutrons.
Answer: C) Electron
10. Which subatomic particle is not found in the nucleus of the atom?
Protons and neutrons are found in the nucleus of an atom, while electrons orbit the nucleus. Electrons are not part of the nucleus.
Answer: C) Electron
