Question

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

Which of the following best explains the position of the two atoms in the periodic table?

A)Both atoms have an estimated Zeff of 1; therefore, Atom D is to the right of Atom E in the same period.

B)Both atoms have Zeff of 1; therefore, Atom D is above Atom E in the same column because of the additional energy level.

C)Atom D has an estimated Zeff of 1 and is therefore to the left of Atom E, which has a Zeff of 9.

D)Atom D has an estimated Zeff of 1 and is therefore below Atom E in the same column, which has a Zeff of 9.

Answer 1

• Option B) Both atoms have Zeff of 1; therefore, Atom D is above Atom E in the same column because of the additional energy level.

Step-by-step explanation:

Zeff means the effective nuclear charge and it is equal to the atomic number (number of protons) less the core electrons (all the electrons less the valence electrons).

• Zeff=number of protons − number of core electrons

Number of core electrons is equal to the total number of protons less the number of valence electrons, so you get:

• Zeff = # protons - (# total electrons - # valence electrons)

Since, the atoms are neutral, # protons = # total electrons, which yields to:

• Zeff = # total electrons - (# total electrons - # valence electrons)

= # total electrons - # total electrons + # valence electrons

= # valence electrons.

So, we have found that Zeff = # valence electrons

In the image, each circle represents a different energy level, with increasing energy when you move away from the nucleus.

The image is showing that both atoms D an E have one valence electron (the only electron is the outermost energy level). Atoms with the same number of valence electrons are in the same column of the periodic table, so both atoms are in the same column and have Zeff of 1 (each circle represents a different energy level, with increasing energy when you move away from the nucleus).

Atom D has fewer energy levels, so it is above atom E in the periodic table.

Hence, you have found that the image is showing that both atoms have Zeff of 1; therefore, Atom D is above Atom E in the same column because of the additional energy level.