Problem 3 - Applied Physics

Question

Which atom is one electron short of having the \(n=2\) energy level filled? Which atom has just one electron in the \(n=3\) energy level?

Step-by-Step Solution

Answer

Fluorine is one electron short of filling \(n=2\), and Sodium has one electron in \(n=3\).

Step 1: Understand electron configuration limits

The energy level \(n=2\) can hold a maximum of 8 electrons (2s and 2p orbitals). Therefore, to be filled, the second energy level must have 8 electrons.

Step 2: Identify element just below filled \(n=2\)

Consider the elements in the periodic table. The element that is one electron short of a full \(n=2\) level, which holds 8 electrons, is Fluorine (F), with an electron configuration of 1s² 2s² 2p⁵. It has 7 electrons in \(n=2\), needing one more to complete the level.

Step 3: Address the \(n=3\) single electron

Now, consider the \(n=3\) level. The element with just one electron in the \(n=3\) energy level is Sodium (Na), which has the electron configuration of 1s² 2s² 2p⁶ 3s¹. Sodium has one electron in the \(n=3\) level.

Key Concepts

Energy Levels in Atoms

When discussing atoms and their properties, understanding energy levels is crucial. Electrons orbit an atom's nucleus in specific shells, known as energy levels. Each energy level can hold a limited number of electrons. For instance, the first energy level (n=1) can hold up to 2 electrons. The second (n=2) can contain up to 8. This is because it has sub-levels: one 2s orbital (which holds 2 electrons) and three 2p orbitals (each can hold 2 electrons, for a total of 6 more electrons). Together, these add up to 8. Think of energy levels like seats in a concert hall's rows. Each row has a specific number of seats, and you must fill these before moving to the next row. Electrons do something similar in atoms, filling lower energy levels first. Knowing how these levels fill helps us predict an atom's properties and behavior.

Periodic Table and Electron Configuration

The periodic table is more than just a list of elements. It's a roadmap to understanding electron configurations. Each element in the periodic table represents atoms with specific electron configurations; these dictate their chemical properties. By following the order on the periodic table, you can determine how electrons fill around a nucleus.

• Elements in the same period have the same number of energy levels.
• Columns, or groups, share similar properties and often similar outer electron configurations.
• This arrangement helps identify elements like Fluorine, which is one electron short of a filled n=2 level.
• It also helps identify Sodium, having just one electron in its n=3 level.

The periodic table is an effective tool in figuring out the configuration of any atom, providing a visual tool to connect electron levels and element behavior.

Atoms and Their Electron Structures

Atoms are the basic building blocks of all matter. They consist of a nucleus, surrounded by a cloud of electrons. The way these electrons are arranged, in what is called the electron configuration, defines how atoms interact and bond with one another. For example, Fluorine has an electron configuration of 1s² 2s² 2p⁵, meaning it has 7 electrons in its second level, one electron short of being filled. Electron configuration affects:

• Chemical reactivity: An atom like Fluorine readily gains one more electron to fill its n=2 level.
• Bonding tendencies: Sodium, with its 1 electron in n=3, often loses this electron to achieve a stable arrangement.
• Overall atomic stability: Atoms tend to move toward a lower energy state, often involving gaining or losing electrons.

Understanding an atom's electron structure is crucial as it determines the atom's properties and how it behaves in reactions.