Question

A monatomic ion has a charge of \(+2 .\) The nucleus of the parent atom has a mass number of \(55 .\) If the number of neutrons in the nucleus is 1.2 times that of the number of protons, what is the name and symbol of the element?

Short answer

The element is manganese, symbolized as \( \text{Mn}^{2+} \).

Step-by-step solution

Define the Number of Neutrons and Protons

The mass number is 55. The number of neutrons is 1.2 times the number of protons. Let the number of protons be denoted as \( p \). Then the number of neutrons is \( 1.2p \). The total number of nucleons (protons + neutrons) is equal to the mass number: \[p + 1.2p = 55\]This simplifies to \( 2.2p = 55 \).

Solve for Number of Protons

Solve the equation from the previous step: \[2.2p = 55\]Divide both sides by 2.2:\[p = \frac{55}{2.2} = 25\]Thus, the number of protons is 25.

Identify the Element and Ion Information

The number of protons determines the element. An atom with 25 protons is manganese (Mn). Since it forms a monatomic ion with a +2 charge, the element is \( \text{Mn}^{2+} \).

Verify the Number of Neutrons

Calculate the number of neutrons to ensure the problem statement is satisfied. If \( p = 25 \), then the number of neutrons is:\[1.2 \times 25 = 30\]Check if total nucleons add to 55:\[25 + 30 = 55\]This confirms that our calculation is correct.

Key concepts

Monatomic Ions

Monatomic ions are ions that consist of just one atom with a positive or negative charge. These ions form when an atom gains or loses electrons, leading to an imbalance between protons and electrons. This imbalance is what gives the ion its charge. For example, a manganese ion with a +2 charge, represented as \( \text{Mn}^{2+} \), has lost two electrons.

When an atom becomes a monatomic ion, its identity doesn't change; it remains the same element, but with a different net charge. The charge is indicated as a superscript after the element's symbol, helping identify how many electrons have been lost or gained.

Understanding monatomic ions is crucial in chemistry because they play vital roles in forming compounds and understanding chemical reactions.

Mass Number

The mass number of an atom is the total count of protons and neutrons in its nucleus. It is an essential property because it helps identify isotopes of an element, which have the same number of protons but differ in the number of neutrons.

For manganese in our example, the mass number is 55. This means that the nucleus contains 55 nucleons in total. The mass number is not the same as the atomic mass found on the periodic table, as the latter is an average of all existing isotopes of an element.

By understanding the mass number, we can calculate the number of neutrons if the number of protons is known, using the formula: - Total nucleons (mass number) = Number of protons + Number of neutrons.

Protons and Neutrons

Protons and neutrons are subatomic particles found in the nucleus of an atom. Protons carry a positive charge, while neutrons are neutral and carry no charge. Together, they make up the mass number of an atom.

The number of protons in an atom is crucial as it defines the element. In the manganese example, there are 25 protons, which identifies the atom as manganese (Mn). This number is also known as the atomic number.

Neutrons add mass to the atom but do not change its chemical identity. They play a role in stabilizing the nucleus. In our example, the number of neutrons is calculated by multiplying the number of protons by 1.2, resulting in 30 neutrons.

Understanding the balance and count of these particles is fundamental in predicting the behavior and stability of an atom.

Chemical Elements

Chemical elements are substances that consist of only one type of atom, characterized by a specific number of protons. The periodic table is a systematic arrangement of all known elements based on their atomic number.

Each element, like manganese (Mn), has unique properties and behaviors. Manganese, identified by having 25 protons, is a transition metal known for forming various oxidation states, which makes it useful in many industrial processes.

Recognizing elements through their number of protons allows chemists to predict chemical reactions and properties. Elements can combine to form compounds, contributing to the vast variety of matter in the universe.

Understanding chemical elements is fundamental in chemistry, as it provides the basis for understanding material composition, reactions, and the formation of new substances.