Question

Some ions do not have a corresponding neutral atom that has the same electron configuration. For each of the following ions, identify the neutral atom that has the same number of electrons and determine if this atom has the same electron configuration. If such an atom does not exist, explain why. (a) \(\mathrm{Cl}^{-}\), (b) \(\mathrm{Sc}^{3+}\), (c) \(\mathrm{Fe}^{2+}\), (d) \(\mathrm{Zn}^{2+}\), (e) \(\mathrm{Sn}^{4+}\).

Short answer

(a) The Chloride ion, \(\mathrm{Cl}^{-}\), has the same electron configuration as the neutral atom Argon (Ar). Their electron configurations are \([Ne] 3s^{2}3p^{6}\). (b) The Scandium ion, \(\mathrm{Sc}^{3+}\), does not have the same electron configuration as the neutral atom Argon (Ar). (c) The Iron ion, \(\mathrm{Fe}^{2+}\), does not have the same electron configuration as the neutral atom Chromium (Cr). (d) The Zinc ion, \(\mathrm{Zn}^{2+}\), does not have the same electron configuration as the neutral atom Nickel (Ni). (e) The Tin ion, \(\mathrm{Sn}^{4+}\), does not have the same electron configuration as the neutral atom Palladium (Pd).

Step-by-step solution

(a) Chloride Ion, \(\mathrm{Cl}^-\)

To find the number of electrons in the chloride ion, first find the atomic number of chlorine (Cl) from the periodic table. Chlorine has an atomic number of 17 (meaning it has 17 electrons in its neutral state). Since the chloride ion gains one electron, it now has 18 electrons. The neutral atom with the same number of electrons as chloride ion is argon (Ar), as argon has 18 electrons. Comparing their electron configurations: Chlorine (Cl): \([Ne] 3s^{2}3p^{5}\) Chloride Ion (\(\mathrm{Cl}^{-}\)): \([Ne] 3s^{2}3p^{6}\) Argon (Ar): \([Ne] 3s^{2}3p^{6}\) Since the electron configuration of chloride ion (\(\mathrm{Cl}^{-}\)) is the same as that of argon (Ar), they have the same electron configuration.

(b) Scandium Ion, \(\mathrm{Sc}^{3+}\)

Scandium (Sc) is found in the periodic table with an atomic number of 21 (21 electrons in its neutral state). The Scandium ion loses three electrons, therefore it has 18 electrons. The neutral atom with the same number of electrons as the scandium ion is argon (Ar), which has 18 electrons. Comparing their electron configurations: Scandium (Sc): \([Ar] 3d^{1}4s^{2}\) Scandium Ion (\(\mathrm{Sc}^{3+}\)): \([Ar]\) Argon (Ar): \([Ne] 3s^{2}3p^{6}\) The electron configuration of the scandium ion (\(\mathrm{Sc}^{3+}\)) differs from argon (Ar), so they do not have the same electron configuration.

(c) Iron Ion, \(\mathrm{Fe}^{2+}\)

From the periodic table, iron (Fe) has an atomic number of 26 (26 electrons in its neutral state). The iron ion loses two electrons, which leaves it with 24 electrons. The neutral atom with the same number of electrons as the iron ion is chromium (Cr), which has 24 electrons. Comparing their electron configurations: Iron (Fe): \([Ar] 3d^{6}4s^{2}\) Iron Ion (\(\mathrm{Fe}^{2+}\)): \([Ar] 3d^{6}\) Chromium (Cr): \([Ar] 3d^{5}4s^{1}\) The electron configuration of the iron ion (\(\mathrm{Fe}^{2+}\)) differs from chromium (Cr), so they do not have the same electron configuration.

(d) Zinc Ion, \(\mathrm{Zn}^{2+}\)

Zinc (Zn) can be found in the periodic table with an atomic number of 30 (30 electrons in its neutral state). The zinc ion loses two electrons, leaving it with 28 electrons. The neutral atom with the same number of electrons as the zinc ion is nickel (Ni), which has 28 electrons. Comparing their electron configurations: Zinc (Zn): \([Ar] 3d^{10}4s^{2}\) Zinc Ion (\(\mathrm{Zn}^{2+}\)): \([Ar] 3d^{10}\) Nickel (Ni): \([Ar] 3d^{8}4s^{2}\) The electron configuration of the zinc ion (\(\mathrm{Zn}^{2+}\)) differs from nickel (Ni), so they do not have the same electron configuration.

(e) Tin Ion, \(\mathrm{Sn}^{4+}\)

Tin (Sn) has an atomic number of 50 (50 electrons in its neutral state) according to the periodic table. The tin ion loses four electrons, which leaves it with 46 electrons. The neutral atom with the same number of electrons as the tin ion is palladium (Pd), which has 46 electrons. Comparing their electron configurations: Tin (Sn): \([Kr] 4d^{10}5s^{2}5p^{2}\) Tin Ion (\(\mathrm{Sn}^{4+}\)): \([Kr] 4d^{10}5s^{2}\) Palladium (Pd): \([Kr] 4d^{10}\) The electron configuration of the tin ion (\(\mathrm{Sn}^{4+}\)) differs from palladium (Pd), so they do not have the same electron configuration.

Key concepts

Ions

Ions are atoms or molecules that have gained or lost electrons, resulting in a net electric charge. There are two main types of ions: cations and anions. Cations are positively charged ions formed by losing one or more electrons, while anions are negatively charged ions formed by gaining electrons. The process of forming ions is crucial in understanding chemical reactions and bonding.

For example, the chloride ion (\( \mathrm{Cl}^- \)) is formed when a neutral chlorine atom gains an extra electron. This gain results in a negative charge, as the number of electrons surpasses that of protons. Identifying ions is important in predicting the properties of elements and their compounds.

Understanding ions helps us analyze the stability, reactivity, and bonding behavior in various chemical contexts. The electron configuration of ions often resembles that of noble gases, achieving the stable electron configuration of fully filled electron shells.

Neutral Atom

A neutral atom is an atom that possesses an equal number of protons and electrons, ensuring no overall charge. This balance between positive (protons) and negative (electrons) charges means the atom is electrically neutral.

For example, a neutral chlorine atom has 17 protons and 17 electrons. When it gains an electron, it forms the chloride ion, an anion with a negative charge. Meanwhile, when atoms lose electrons, they form cations with a positive charge, like the zinc ion (\( \mathrm{Zn}^{2+} \)).Understanding neutral atoms is foundational in chemistry, as it lays down the groundwork for studying how atoms interact with each other through exchanging or sharing electrons. This concept is particularly significant when heeding to ions' formation and predicting possible chemical reactions.

Periodic Table

The periodic table is a structured arrangement of the chemical elements, organized in increasing order of atomic numbers. It provides a comprehensive layout that aids in understanding the general properties of elements and predicting their behaviors.

The periodic table is divided into groups and periods. Elements in the same group (column) usually have similar chemical properties due to similar valence electron configurations. For instance, elements in Group 1, like lithium and sodium, are highly reactive metals known as alkali metals.

Observing the position of an element on the periodic table helps us determine its atomic number, natural state, and potential ionization behavior. For example, scandium (\( \mathrm{Sc} \)) is found in Group 3, indicating it commonly forms ions by losing electrons from its outer shell, as seen in the scandium ion (\( \mathrm{Sc}^{3+} \)). The periodic table is an essential tool in the study of chemistry, allowing for the systematic exploration of elements.

Atomic Number

The atomic number of an element is one of the most fundamental properties, representing the number of protons in the nucleus of an atom. This number is unique to each element and determines its identity.

For instance, chlorine has an atomic number of 17, meaning each chlorine atom has 17 protons. Consequently, in a neutral atom, chlorine also has 17 electrons. The atomic number is crucial not only for identifying the element but also for understanding its placement in the periodic table.

The atomic number helps predict several properties of the element, such as its valency, type of ion it may form, and its chemical reactivity. Knowing the atomic number aids in sketching the electron configuration of an atom or ion, which is key to analyzing chemical behavior and bonding tendencies. As seen across various examples like zinc (\( \mathrm{Zn} \) with atomic number 30) or iron (\( \mathrm{Fe} \) with atomic number 26), the atomic number elucidates critical aspects of elemental chemistry.