AP Physics 2 Exam Question:

Consider an atom with atomic number 8.

(a) Calculate the mass number of this atom.

(b) Determine the number of protons, neutrons, and electrons in this atom.

(c) Calculate the total charge on this atom.

(d) Identify the electron configuration of this atom.

Answer:

(a) The atomic number (Z) represents the number of protons in an atom. Given that the atomic number is 8, the mass number (A) can be calculated as follows:

   A = Z + Number of neutrons

To find the number of neutrons, we need to subtract the atomic number from the mass number.

   A = 8 + Number of neutrons
   Number of neutrons = A - 8

Since the question does not provide the mass number (A), we cannot provide a specific value. However, we can conclude that the mass number will be greater than or equal to 8.

(b) The number of protons is equal to the atomic number, so there are 8 protons in this atom.

To find the number of electrons, we need to know if the atom is neutral or if it has a charge. Since the question does not specify, we will assume it is a neutral atom. In a neutral atom, the number of electrons is equal to the number of protons, so there are 8 electrons.

To find the number of neutrons, we can use the result from part (a):

   Number of neutrons = A - 8

(c) The total charge on an atom is determined by the difference between the number of protons and the number of electrons. In a neutral atom, the total charge is zero.

   Total charge = Number of protons - Number of electrons
               = 8 - 8
               = 0

Thus, the total charge on this atom is 0.

(d) The electron configuration provides information about the arrangement of electrons in atomic orbitals. The electron configuration of an atom with atomic number 8 (oxygen) is:

   1s^2 2s^2 2p^4

This configuration indicates that there are 2 electrons in the 1s orbital, 2 electrons in the 2s orbital, and 4 electrons in the 2p orbital.

In summary, for an atom with atomic number 8: (a) The mass number will be greater than or equal to 8. (b) The number of protons is 8, the number of neutrons depends on the mass number, and the number of electrons is 8. (c) The total charge on the atom is 0. (d) The electron configuration is 1s^2 2s^2 2p^4.