Problem 105 - Introductory Chemistry Atoms First

Question

How many electrons are there in Br'? What \(1+\) cation has the same number of electrons as Br"?

Step-by-Step Solution

Answer

The Br^(-) ion has 36 electrons. The 1+ cation with the same number of electrons is Br^(+).

Step 1: Find the atomic number of Bromine

To find the number of electrons in a Br^(-) ion, first, we should know the atomic number of Bromine. The atomic number of Bromine (Br) is 35, which represents the number of protons and electrons in a neutral atom.

Step 2: Determine the number of electrons in Br^(-) ion

Since the ion has a -1 charge, it means it has gained one additional electron compared to a neutral Br atom. Therefore, the total number of electrons in a Br^(-) ion is the atomic number of Bromine (35) plus the extra electron from the negative charge: 35 + 1 = 36 electrons

Step 3: Find a 1+ cation with the same number of electrons

We are looking for an ion with a +1 charge and 36 electrons. To find this ion, we need a neutral atom that has one less electron than Br^(-). A neutral atom with 35 electrons has an atomic number of 36 - 1 = 35. The element with an atomic number of 35 is Bromine (Br). If Bromine loses one electron, it will have a +1 charge and the same number of electrons as a Br^(-) ion. So the 1+ cation with 36 electrons is Br^(+).

Key Concepts

Atomic Number

The atomic number is a fundamental property of an element, symbolizing the number of protons found in the nucleus of its atoms.
This number uniquely identifies a chemical element and also defines its position in the periodic table.
For a neutral atom, the atomic number equals the number of electrons orbiting the atom.

In the case of bromine, its atomic number is 35.

• This indicates that a neutral bromine atom has 35 protons and 35 electrons.

The atomic number is pivotal in determining the element's identity and is key to locating it on the periodic table.
Understanding atomic numbers helps predict the chemical behavior of elements by acknowledging their electron arrangement.
By knowing the atomic number, one can also infer an element's reactivity and bonding characteristics.

Bromine Ion

An ion is formed when an atom gains or loses electrons, acquiring a charge in the process. Bromine can form a bromide ion, denoted as Br⁻, by gaining an extra electron.
This results in a negatively charged ion.

• A neutral bromine atom has 35 electrons.
• When it gains one additional electron, the total count becomes 36, resulting in Br⁻.

This gain of an electron is characteristic of nonmetals, which often form anions. The formation of a bromide ion is an example of how electron configurations change with charge, impacting atomic size and other properties.
This stabilized electron configuration of Br⁻ is analogous to the electron configuration of a noble gas.

Electron Count

The electron count in an atom or ion is crucial to understanding its properties and behavior.
For bromine, it is the starting point in establishing how the element interacts chemically.
Electrons are arranged in shells or orbitals, and stability is often achieved by having full outer shells.

For Br⁻:

• There are 36 electrons.
• The extra electron gained gives it a stable noble gas configuration.

Electrons determine how an element bonds and reacts.
The difference in electron loss or gain will result in ions with varied chemical properties compared to their neutral atom forms. By understanding electron count, one gains insight into reactivity, electricity conduction, and overall chemical characteristics.

Cation with Same Electrons

A cation is formed when an atom loses electrons, resulting in a positive charge.
To find a cation with the same number of electrons as a bromide ion (Br⁻) which has 36 electrons, consider neutral atoms with one electron fewer.

• A neutral atom with 35 electrons is bromine (atomic number 35).
• When bromine forms Br⁺, by losing an electron, it becomes a cation with 36 electrons, matching the electron count of Br⁻.

This illustrates that elements can form ions of both charges, impacting their role in reactions and compounds. Matching electron counts between ions means they share similar electron configurations, leading to similarities in stability and chemical behavior. Understanding these transformations deepens our comprehension of periodic trends and reactivities.