Conversion of a neutral atom into an anion

When a neutral atom gains one or more electrons, it becomes negatively charged and forms an anion. This process is known as ionization. Let's explore the changes that occur when a neutral atom is converted into an anion:

Atomic Structure
- An atom consists of a positively charged nucleus and negatively charged electrons orbiting around it.
- The atomic number of an atom is determined by the number of protons in its nucleus, which also defines its identity.
- The number of electrons in a neutral atom is equal to the number of protons, resulting in a neutral charge.

Formation of an Anion
- When a neutral atom gains one or more electrons, it becomes negatively charged and forms an anion. The gained electrons occupy the outermost energy level or shell of the atom, known as the valence shell.
- The valence shell is the outermost shell of an atom and determines its reactivity and chemical properties.
- By gaining electrons, the anion achieves a stable electron configuration similar to that of a noble gas, resulting in increased stability.

Changes in Size
- When a neutral atom gains an electron, the electron-electron repulsion increases within the valence shell. This causes the electron cloud to expand, resulting in an increase in the size of the anion compared to the neutral atom.
- The size increase occurs because the added electron(s) occupy more space in the valence shell, pushing other electrons farther away from the nucleus.
- Hence, when a neutral atom is converted into an anion, its size increases.

Changes in Atomic Number
- The atomic number of an element remains the same when it forms an anion. The atomic number is determined by the number of protons present in the nucleus, and gaining or losing electrons does not alter this value.
- Therefore, the atomic number of an atom does not change when it is converted into an anion.

In conclusion, when a neutral atom is converted into an anion, its size increases due to the expansion of the electron cloud in the valence shell. However, the atomic number remains the same as it is determined by the number of protons in the nucleus.

Explanation:
When a neutral atom is converted into an anion, it means that the atom gains one or more electrons. This results in the following changes:
Size increase:
- The addition of electrons leads to an increase in the electron-electron repulsion within the atom.
- This repulsion causes the electron cloud to expand, resulting in an increase in the size of the anion compared to the neutral atom.
Atomic number decreases:
- The atomic number of an atom is determined by the number of protons in its nucleus.
- When an atom gains one or more electrons to become an anion, the number of protons remains the same, but the number of electrons increases.
- As a result, the atomic number of the anion remains the same as the neutral atom.
Therefore, the correct answer is D: Atomic number decreases.