Question

For an isolated atom, why do we expect the number of electrons present in the atom to be the same as the number of protons in the nucleus of the atom?

Short answer

In an isolated atom, the total positive charge of protons in the nucleus must be exactly balanced by the total negative charge of electrons orbiting around it to achieve charge neutrality, which is a state with a net charge of zero. Since protons and electrons have equal but opposite charges, the number of electrons must be equal to the number of protons to maintain this neutrality. If there were an imbalance in the number of protons and electrons, the atom would not be neutral, contradicting the properties of an isolated atom.

Step-by-step solution

Understand the properties of an isolated atom

An isolated atom is an atom that is not interacting with other atoms or molecules. It has a central nucleus, composed of protons and neutrons, and electrons orbiting around the nucleus at distinct energy levels.

Identify the charges of protons and electrons

Protons, located in the nucleus, carry a positive charge (+1e), while electrons, orbiting around the nucleus, carry a negative charge (-1e). Both have the same magnitude of charge, but opposite signs.

Explain charge neutrality

In an isolated atom, there is no external force or influence affecting its charge. Therefore, such atoms must have a net charge of zero, meaning that the total positive charge of the protons must be exactly balanced by the total negative charge of the electrons. This state is known as charge neutrality.

Demonstrate why the number of electrons must equal the number of protons

Since the charges of protons and electrons are equal in magnitude but opposite in sign, the only way for an isolated atom to achieve charge neutrality is for the number of electrons to be equal to the number of protons. If there were more protons than electrons, the atom would have a net positive charge; if there were more electrons than protons, it would have a net negative charge. In both cases, the atom would not be neutral, contradicting the fact that an isolated atom must have a net charge of zero. Therefore, we expect the number of electrons in an isolated atom to be the same as the number of protons in its nucleus to maintain charge neutrality.

Key concepts

Charge Neutrality

Atoms strive to achieve a balanced state where they have no overall electric charge. This is what we call charge neutrality. Simply put, for an atom to be charge neutral, the positive charges must perfectly match the negative charges.

The positive charges come from protons, which are found in the nucleus, and each proton carries a charge of +1. Electrons, on the other hand, carry negative charges of -1 each. In a charge-neutral atom, the number of protons and electrons is the same, ensuring the total positive charge balances out the total negative charge.

• Positive charge from protons = +1 each
• Negative charge from electrons = -1 each
• Charge neutrality: total positive = total negative

If an atom has an unequal number of protons and electrons, it will not be neutral. Instead, it would have a net charge, making it an ion rather than an atom.

Protons and Electrons

To fully understand atomic structure, it is vital to know about protons and electrons. Protons reside in the nucleus and have a charge of +1. They are relatively large compared to electrons and play a crucial role in determining the identity and characteristics of an element.

Electrons, in contrast, are tiny and orbit the nucleus. They carry a -1 charge. Although they are small, electrons are dynamic and can move between energy levels around the nucleus.

• Protons = found in the nucleus, charge of +1
• Electrons = orbit the nucleus, charge of -1
• Both have equal, but opposite, charges

The number of protons in an atom determines the element itself, while the number of electrons often affects how the atom interacts with others. In an isolated atom, having an equal number of protons and electrons results in a neutral charge, an essential concept in chemistry.

Isolated Atom

An isolated atom is a single atom that exists by itself without interacting with any other atoms or molecules. This concept is significant because, in this state, the atom's properties can be considered without the influence of external forces.

This means for an isolated atom, the conditions needed for charge neutrality are purely internal. The atom doesn’t lose or gain electrons from neighboring atoms, ensuring its protons and electrons remain equal in number.

• Exist without interactions
• Balanced numbers of protons and electrons
• No external influence on charge

For the isolated atom to maintain a neutral state, it must inherently balance its charges internally, underscoring why the number of electrons equals the number of protons. This simplicity is why isolated atoms serve as a foundational concept in understanding atomic structure and chemistry.