Question

An element forms an ionic compound with chlorine, leading to a compound having the formula \(\mathrm{XCl}_{2}\) The ion of element \(X\) has mass number 89 and 36 electrons. Identify the element \(X,\) tell how many neutrons it has, and name the compound.

Short answer

Element X is strontium (Sr) with an atomic number of 38. It has 51 neutrons in its ion form, and the compound formed with chlorine is called strontium chloride (\(\mathrm{SrCl}_{2}\)).

Step-by-step solution

Since element X forms an ionic compound with chlorine (\(\mathrm{XCl}_{2}\)), the ion of element X lost 2 electrons to form a charge of +2. To find the atomic number of element X, we need to add those 2 electrons back to the ion's 36 electrons, resulting in 38. The atomic number of element X is 38. #Step 2: Identify the element X based on its atomic number#

Using the periodic table, we can identify the element with an atomic number of 38 as strontium (Sr). #Step 3: Calculate the number of neutrons in the ion of element X#

We know the mass number (sum of protons and neutrons) for the ion as 89. Since its atomic number is 38 and the number of protons is equal to the atomic number, we can find the number of neutrons by subtracting the number of protons from the mass number: \(89 - 38 = 51\). Therefore, the ion of element X has 51 neutrons. #Step 4: Name the ionic compound#

The ionic compound consists of strontium (Sr) and chlorine (Cl). The compound has a formula of \(\mathrm{SrCl}_{2}\). In the compound's name, the cation, strontium, remains unchanged, while the chloride anion is derived from the name of the nonmetal element, chlorine. As a result, the compound's name is strontium chloride. To summarize the solution: Element X is strontium (Sr), having an atomic number of 38. It has 51 neutrons in its ion form, and the compound formed with chlorine is called strontium chloride (\(\mathrm{SrCl}_{2}\)).

Key concepts

Element Identification

Identifying elements correctly is quintessential in the study of chemistry.
Every element can be uniquely identified by its atomic number—the number of protons in the nucleus of its atoms. In the exercise, the identification of element X was deduced by analyzing its ionic compound and using the given electron information. Since element X formed an ionic bond with chlorine, losing two electrons, and resulting in 36 electrons, we could infer that the neutral element had two additional electrons, leading to an atomic number of 38.

This atomic number is like the element’s ID card, ensuring that no two elements share the same one. Knowing the atomic number, we are able to look up the element in the periodic table—a crucial step in the element identification process.

Periodic Table

The periodic table is a systematic arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties.
This tabular display enables chemists to understand the relationships between the properties of elements and to predict the characteristics of new elements that might be discovered or synthesized. In our example, by knowing the atomic number of 38, we used the periodic table to find that the element is strontium (Sr).

Understanding the Periodic Table

Elements in the periodic table are arranged in rows called periods and columns known as groups or families. Elements within the same group tend to exhibit similar physical and chemical properties. For instance, all elements in group 1 (except hydrogen) are alkali metals, which are highly reactive and have a single electron in their outer shell.

Atomic Structure

The foundation of chemical identities lies in atomic structure. All matter is made of atoms, and an atom's structure includes a nucleus made of protons and neutrons, with electrons orbiting this nucleus.
The number of protons (the atomic number) defines what element the atom is, while the mass number, the total number of protons and neutrons, gives us an idea of its isotopic composition. In the exercise, element X had an ion with a mass number of 89 and 36 electrons, which indicated that normally, the element would have 38 protons.

With the atomic number and mass number at hand, the number of neutrons was calculated by subtracting the atomic number from the mass number, which is essential to understand isotopes and radionuclides in advanced chemistry topics.

Chemical Formulas

Understanding chemical formulas is critical as they provide the proportions of elements in a compound and the structure of the compound.
A formula such as \(\mathrm{XCl}_{2}\), indicates that for every atom of element X, there are two atoms of chlorine. This stoichiometric information is vital for balancing chemical equations and in carrying out calculations related to chemical reactions. In our exercise, the identification of element X as strontium (Sr) led to the chemical formula being \(\mathrm{SrCl}_{2}\), which is known as strontium chloride.

These formulas guide us in predicting the properties of new compounds and are fundamental in chemical nomenclature. Without understanding chemical formulas, we wouldn't be able to communicate effectively in the language of chemistry or replicate studies and experiments accurately.