Question

For each of the following ions, indicate the number of protons and electrons the ion contains. a. \(\quad \mathrm{Ba}^{2+}\) b. \(\mathrm{Zn}^{2+}\) c. \(\mathrm{N}^{3-}\) d. \(\mathrm{Rb}^{+}\) e. \(\mathrm{Co}^{3+}\) f. \(\mathrm{Te}^{2-}\) g. \(\mathrm{Br}^{-}\)

Short answer

a. \(\mathrm{Ba}^{2+}\): 56 protons, 54 electrons b. \(\mathrm{Zn}^{2+}\): 30 protons, 28 electrons c. \(\mathrm{N}^{3-}\): 7 protons, 10 electrons d. \(\mathrm{Rb}^{+}\): 37 protons, 36 electrons e. \(\mathrm{Co}^{3+}\): 27 protons, 24 electrons f. \(\mathrm{Te}^{2-}\): 52 protons, 54 electrons g. \(\mathrm{Br}^{-}\): 35 protons, 36 electrons

Step-by-step solution

Consult the Periodic Table for Number of Protons

To determine the number of protons in the different elements, consult the periodic table. Next to each element's symbol, you will find the atomic number (whole number), which represents the number of protons in an atom of that element.

Determine the Number of Protons and Electrons

To determine the number of protons and electrons in each ion, consider the charge of the ion. The charge of the ion indicates how many electrons have been added or removed from a neutral atom. If the charge is positive, that means electrons are removed, and if the charge is negative, it means electrons are added. a. For \(\mathrm{Ba}^{2+}\), the atomic number of Ba (Barium) is 56, so: - Protons: 56 - Electrons: 56 - 2 = 54 b. For \(\mathrm{Zn}^{2+}\), the atomic number of Zn (Zinc) is 30, so: - Protons: 30 - Electrons: 30 - 2 = 28 c. For \(\mathrm{N}^{3-}\), the atomic number of N (Nitrogen) is 7, so: - Protons: 7 - Electrons: 7 + 3 = 10 d. For \(\mathrm{Rb}^{+}\), the atomic number of Rb (Rubidium) is 37, so: - Protons: 37 - Electrons: 37 - 1 = 36 e. For \(\mathrm{Co}^{3+}\), the atomic number of Co (Cobalt) is 27, so: - Protons: 27 - Electrons: 27 - 3 = 24 f. For \(\mathrm{Te}^{2-}\), the atomic number of Te (Tellurium) is 52, so: - Protons: 52 - Electrons: 52 + 2 = 54 g. For \(\mathrm{Br}^{-}\), the atomic number of Br (Bromine) is 35, so: - Protons: 35 - Electrons: 35 + 1 = 36

Key concepts

Protons

Protons are positively charged particles found in the nucleus of an atom. These tiny particles play a critical role in defining the identity of an element. The number of protons within an atom is known as the atomic number.

The atomic number is significant as it determines the element's position in the periodic table. For example, hydrogen, the first element on the periodic table, has one proton, while helium, the second element, has two protons. This atomic number is a unique identifier for each element.

• If an atom has two protons, it is always helium.
• If an atom has three protons, it must be lithium.

Atoms can gain or lose electrons, turning them into ions, but the number of protons does not change during this process. Thus, for ions, the number of protons remains equal to the atomic number of the element.

Electrons

Electrons are small particles with a negative charge that orbit the nucleus of an atom. In a neutral atom, the number of electrons equals the number of protons, balancing the positive and negative charges.

Ions differ because their number of electrons changes based on their charge:

• Positive ions (cations) result from losing electrons, leading to more protons than electrons.
• Negative ions (anions) result from gaining electrons, leading to more electrons than protons.

Consider an ion like \( ext{Ba}^{2+} \): it indicates that the barium ion has lost two electrons, hence fewer electrons than a neutral barium atom.For \( ext{N}^{3-} \), the nitrogen ion gained three electrons, resulting in an overall negative charge. The electron count is crucial in determining the ion's overall charge and chemical behavior.

Periodic Table

The periodic table is a comprehensive chart that organizes all known elements according to their atomic number, electron configuration, and recurring chemical properties. It serves as an essential tool for chemists and students to quickly locate information about elements.

Every element on the table is identified by its unique atomic number, which corresponds to the number of protons in each atom of the element. This allows for easy determination of key properties:

• The position of each element correlates with its electron configuration, influencing its chemistry.
• Groups or columns typically share similar properties, like reactivity or metallic nature.

For tasks like determining ion characteristics, the periodic table helps find the atomic numbers and therefore, the counts of protons and electrons necessary to understand ions. By consulting the periodic table, one can easily find that barium (Ba) has an atomic number of 56, zinc (Zn) has 30, and so on. These numbers are foundational in calculating the electron count in ions.