Question

How many electrons are present in each of the following ions? a. \(\mathrm{Ba}^{2+}\) b. \(\mathrm{P}^{3-}\) c. \(\mathrm{Mn}^{2+}\) d. \(\mathrm{Mg}^{2+}\) e. \(\mathrm{Cs}^{+}\) f. \(\mathrm{Pb}^{2+}\)

Short answer

The number of electrons in each ion is: a. \(\mathrm{Ba}^{2+}\): 54 electrons b. \(\mathrm{P}^{3-}\): 18 electrons c. \(\mathrm{Mn}^{2+}\): 23 electrons d. \(\mathrm{Mg}^{2+}\): 10 electrons e. \(\mathrm{Cs}^{+}\): 54 electrons f. \(\mathrm{Pb}^{2+}\): 80 electrons

Step-by-step solution

Determine the number of protons

: Look up the atomic number of each element on the periodic table. The atomic number is the number of protons in a neutral atom of that element. a. Ba: Atomic number = 56 protons b. P: Atomic number = 15 protons c. Mn: Atomic number = 25 protons d. Mg: Atomic number = 12 protons e. Cs: Atomic number = 55 protons f. Pb: Atomic number = 82 protons

Add or subtract the charge to determine the number of electrons

: Since a positive charge indicates lost electrons and a negative charge indicates gained electrons, add or subtract the ion's charge from the number of protons to find the number of electrons. a. \(\mathrm{Ba}^{2+}\): 56 protons - 2 = 54 electrons b. \(\mathrm{P}^{3-}\): 15 protons + 3 = 18 electrons c. \(\mathrm{Mn}^{2+}\): 25 protons - 2 = 23 electrons d. \(\mathrm{Mg}^{2+}\): 12 protons - 2 = 10 electrons e. \(\mathrm{Cs}^{+}\): 55 protons - 1 = 54 electrons f. \(\mathrm{Pb}^{2+}\): 82 protons - 2 = 80 electrons The number of electrons in each ion is: a. \(\mathrm{Ba}^{2+}\): 54 electrons b. \(\mathrm{P}^{3-}\): 18 electrons c. \(\mathrm{Mn}^{2+}\): 23 electrons d. \(\mathrm{Mg}^{2+}\): 10 electrons e. \(\mathrm{Cs}^{+}\): 54 electrons f. \(\mathrm{Pb}^{2+}\): 80 electrons

Key concepts

Atomic Number

The atomic number of an element is one of its most fundamental properties. Simply put, it is the number of protons found in the nucleus of an atom. Protons are positively charged particles, and the atomic number also tells us about the number of electrons in a neutral atom since atoms are electrically neutral overall. The number of electrons can vary in an ionized atom which affects its chemical properties.

For instance, if we have barium (Ba) with an atomic number of 56, it means a neutral barium atom contains 56 protons and 56 electrons. The atomic number is key to understanding the electron configuration in ions as it sets the baseline of electrons before ionization.

Periodic Table

The periodic table is not just a tool for categorizing elements; it's a roadmap of the elements, outlining their properties, such as atomic number and valence electron configurations. It's structured so that elements with similar properties fall into the same columns, known as groups. This organization assists in predicting the behavior of atoms during chemical reactions, including their ionization tendencies.

For example, in the problem given, magnesium (Mg) is found in group 2, which means it has two valence electrons that it tends to lose to become stable, resulting in a commonly formed \( \mathrm{Mg}^{2+} \) ion. Thus, the periodic table helps predict the charge of ions based on their position.

Ion Charge

Ion charge is the electric charge an atom acquires when it gains or loses electrons to form an ion. Metals tend to lose electrons and form positively charged ions or cations, while nonmetals tend to gain electrons and form negatively charged ions or anions. The size of the charge corresponds to the number of electrons lost or gained.

In our exercise, phosphorus (P), typically a nonmetal, gains three electrons to form a \( \mathrm{P}^{3-} \) ion. The '3-' signifies the gain of three electrons compared to the number of protons. Understanding ion charge is crucial for predicting chemical formulas, naming compounds, and balancing chemical equations.

Protons and Electrons

Protons and electrons are subatomic particles with opposite charges but have an important relationship in atom stability. Protons possess a positive charge, and electrons carry a negative charge. In a neutral atom, the number of protons equals the number of electrons, canceling out their charges and leading to electrical neutrality. However, when atoms form ions, this balance is disrupted.

• An ion with more protons than electrons carries a positive charge, such as the \( \mathrm{Ba}^{2+} \) ion with 56 protons and 54 electrons.
• An ion with fewer protons than electrons carries a negative charge, such as the \( \mathrm{P}^{3-} \) ion with 15 protons and 18 electrons.

The concept of protons and electrons is integral to defining the structure of ions and their interactions in chemistry.