Question

The image compares the arrangement of electrons in two different neutral atoms.

"A figure labeled Atom Q has a shaded sphere at the center of three concentric circles. The innermost circle has two black spheres. The middle circle has six black spheres. To the left of this figure is another figure labeled Atom P. Atom P has a shaded sphere at the center of three concentric circles. The innermost circle has two black spheres. The middle circle has seven black spheres.
Which of the following best explains the position of the two atoms in the periodic table?
Select one:
a. Atom P has an estimated Zeff of 7 and is therefore to the left of Atom Q, which has a Zeff of 6.
b. Atom P has an estimated Zeff of 7 and is therefore to the right of Atom Q, which has a Zeff of 6.
c. Atom P has an estimated Zeff of 5 and is therefore below Atom Q, which has a Zeff of 4.
d. Atom P has an estimated Zeff of 5 and is therefore above Atom Q, which has a Zeff of 4.

Answer 1

b

Step-by-step explanation:

Answer 2

• Option b. Atom P has an estimated Zeff of 7 and is therefore to the right of Atom Q, which has a Zeff of 6.

Step-by-step explanation:

Please, find attached the figures of both atom Q and atom P corresponding to this question.

The features of atom Q are:

• Each black sphere represents an electron

• In total this atom has 8 electrons: 2 in the inner shell and 6 in the outermost shell.

• Since it is assumed that the atom is neutral, it has 8 protons: one positive charge of a proton balances one negative charge of an electron. Thus, the atomic number of this atom is 8.

• Since only two shells are ocuppied, you can assert that the atom belongs to the period 2 (which is confirmed looking into a periodic table with the atomic number 8).

• Zeff is the effective nuclear charge of the atom. It accounts for the net positive charge the valence electrons experience. And may, in a very roughly way, be estimated as the number of protons less the number of electrons in the inner shells. Thus, for this atom, an estimated Z eff = 8 - 2 = 6.

The features of atom P are:

• Again, each black sphere represents an electron

• In total this atom has 9 electrons: 2 in the inner shell and 7 in the outermost shell.

• Since it is assumed that the atom is neutral, it has 9 protons.

• The atomic number of this atom is 9.

• Using the same reasoning used for atom Q, this atom is also in the period 2.

• Estimated Z eff = 9 - 2 = 7.

Then, since atom P has a greater Z eff than atom Q (an estimated Zeff of 7 for atom P against an estimated Z eff of 6 for atom Q), and both atoms are in the same period, you can affirm that atom P has a greater atomic number and is therefore to the right of atom Q.