Question

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

Answer 1

Answer:

• 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.

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.