Problem 36 - Chemistry The Molecular Nature of Matter

Question

How many electrons has a nitrogen atom gained if it has formed the ion \(\mathrm{N}^{3-}\) ? How many protons and electrons are in an \(\mathrm{N}^{3-}\) ion?

Step-by-Step Solution

Answer

The nitrogen atom has gained 3 electrons to form the \(\mathrm{N}^{3-}\) ion. Thus, an \(\mathrm{N}^{3-}\) ion has 10 electrons and 7 protons.

Step 1: Understanding Nitrogen Ion Charge

The notation \(\mathrm{N}^{3-}\) represents a nitrogen ion with a charge of -3. This means the nitrogen atom has gained 3 additional electrons compared to its neutral state, as electrons are negatively charged.

Step 2: Calculating Electrons in Nitrogen Ion

In its neutral state, nitrogen has 7 electrons. Since it has gained 3 electrons to become \(\mathrm{N}^{3-}\), it now has 7 (original electrons) + 3 (extra electrons) = 10 electrons.

Step 3: Determining Protons in Nitrogen Ion

The number of protons in an atom is determined by its atomic number, which does not change when an atom forms an ion. The atomic number of nitrogen is 7, so the \(\mathrm{N}^{3-}\) ion has 7 protons.

Key Concepts

Ionic Charge

When an atom gains or loses electrons, it becomes an ion. This results in the formation of an ionic charge, which is an electrical charge due to the loss or gain of electrons. In the case of the nitrogen ion (N^{3-}), the '3-' indicates that the atom has gained three additional electrons. These additional electrons create a negative charge because electrons carry a negative charge. It's essential to understand that the ionic charge does not affect the protons in the atom; it solely reflects the change in the number of electrons.

Through this charge notation, one can instantly deduce not only the number of electrons gained or lost but also the overall charge of the ion, which is critical in predicting how the ion will interact with other ions and molecules in chemical reactions. For example, ions with opposite charges are generally attracted to each other and may form ionic bonds.

Atomic Number

The atomic number of an element is a fundamental concept in chemistry, providing vital information about its identity and properties. It is designated as the number of protons in the nucleus of an atom and is unique to each element. For nitrogen, with an atomic number of 7, it always contains 7 protons, regardless of its state. This number is constant even when nitrogen forms ions.

The significance of the atomic number extends beyond counting protons; it also implies the number of electrons in a neutral atom. However, when discussing ions, the number of electrons can differ from the atomic number, as seen with the nitrogen ion (N^{3-}). Understanding the atomic number helps us correctly identify elements and predict their chemical behavior based on their placement in the periodic table.

Electrons and Protons in Ions

Ions are formed when atoms gain or lose electrons, resulting in a net charge. It is important to distinguish between the number of protons and electrons in ions because this determines their ionic charge. Protons are located in the atom's nucleus and, as mentioned earlier, their number remains unchanged during ion formation, being equal to the element's atomic number. Electrons, on the other hand, reside in the electron cloud surrounding the nucleus and are responsible for the atom's electrical properties.

In the case of a (N^{3-}) ion, although the number of protons remains consistent at 7, reflecting nitrogen's atomic number, the number of electrons has increased from the neutral atom's count due to the gain of three additional electrons. Therefore, this ion has 10 electrons (7 original plus 3 additional). This distinction between protons and electrons is what defines the character of the ion and dictates how it will interact with its environment, such as the formation of ionic compounds with other elements.