Question

Write each element’s orbital notation and complete electron configuration. a. beryllium c. nitrogen b. aluminum d. sodium

Short answer

a. Beryllium (Be): \[ [He]2s^2 \, ; \, 1s\downarrow\uparrow \, 2s\downarrow\uparrow \] b. Aluminum (Al): \[ [Ne]3s^2 3p^1 \, ; \, 1s\downarrow\uparrow \, 2s\downarrow\uparrow \, 2p\downarrow\uparrow\downarrow\uparrow\downarrow\uparrow \, 3s\downarrow\uparrow \, 3p\downarrow \] c. Nitrogen (N): \[ [He]2s^2 2p^3 \, ; \, 1s\downarrow\uparrow \, 2s\downarrow\uparrow \, 2p\downarrow\uparrow\downarrow\uparrow\downarrow \] d. Sodium (Na): \[ [Ne]3s^1 \, ; \, 1s\downarrow\uparrow \, 2s\downarrow\uparrow \, 2p\downarrow\uparrow\downarrow\uparrow\downarrow\uparrow \, 3s\downarrow \]

Step-by-step solution

Determine the atomic numbers of the elements

To find the electron configuration of an element, we need to determine the number of electrons, which is equal to the atomic number of the element. We can find the atomic numbers from the periodic table. a. Beryllium (Be): Atomic number = 4 b. Aluminum (Al): Atomic number = 13 c. Nitrogen (N): Atomic number = 7 d. Sodium (Na): Atomic number = 11

Fill in the electron orbitals

Now, we have to fill in the electron orbitals systematically according to the aufbau principle. We can use the Mnemonic rule to help remember the correct order in which to fill orbitals: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on. a. Beryllium (Be): 1s^2 2s^2 b. Aluminum (Al): 1s^2 2s^2 2p^6 3s^2 3p^1 c. Nitrogen (N): 1s^2 2s^2 2p^3 d. Sodium (Na): 1s^2 2s^2 2p^6 3s^1

Write the complete electron configuration using the noble gas shorthand

Next, we will write the complete electron configurations using the noble gas shorthand, which is a way to represent the electron configuration more compactly by expressing the inner electrons using the noble gas configuration of the previous row in the periodic table. a. Beryllium (Be): [He] 2s^2 b. Aluminum (Al): [Ne] 3s^2 3p^1 c. Nitrogen (N): [He] 2s^2 2p^3 d. Sodium (Na): [Ne] 3s^1

Write the orbital notations

finally, we will write the orbital notations, which represent the electron configurations visually. We will draw boxes for each orbital and use arrows to represent the electrons inside them. a. Beryllium (Be): 1s↓↑ 2s↓↑ b. Aluminum (Al): 1s↓↑ 2s↓↑ 2p↓↑↓↑↓↑ 3s↓↑ 3p↓ c. Nitrogen (N): 1s↓↑ 2s↓↑ 2p↓↑↓↑↓ d. Sodium (Na): 1s↓↑ 2s↓↑ 2p↓↑↓↑↓↑ 3s↓

Key concepts

Orbital Notation

Orbital notation is a visual method to represent electron configurations in atoms. It helps in illustrating the orbitals that electrons occupy. To express this, boxes (or lines) for orbitals are drawn with arrows indicating the electrons. The direction of the arrow (up or down) shows the spin of each electron.

For instance, consider nitrogen (N) with an atomic number of 7. Its orbital notation would be:
1s↓↑ 2s↓↑ 2p↓↑↓↑↓. Each box represents an orbital, and each orbital can hold two electrons, signified by the opposing arrows. The presence of paired and unpaired electrons is critical for understanding the magnetic properties and chemical reactivity of an element.

Aufbau Principle

The aufbau principle is a fundamental rule used to determine an element's electron configuration. It states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. This means that electrons are added one at a time to the 'house' of the atom, starting at the ground floor (1s orbital) and moving upwards (2s, 2p, etc.).

For example, when filling in the orbitals for aluminum (Al), we start with the 1s orbital, then the 2s, followed by the 2p, and so on, resulting in the configuration: 1s² 2s² 2p⁶ 3s² 3p¹. The sequence of orbital filling is vital to accurately predicting and drawing the orbital notation for any given element.

Noble Gas Shorthand

The noble gas shorthand, also known as the noble gas core notation, simplifies writing electron configurations by using the electron configuration of the nearest noble gas from the preceding period to represent core electrons. This method acknowledges that the core electrons (those located in the inner shells) have the same configuration as those of the nearest noble gas.

For beryllium (Be), which has an atomic number of 4, the noble gas prior to it is helium (He). Beryllium's noble gas shorthand is [He] 2s², indicating that the first two electrons are in the same configuration as helium, and the remaining two occupy the 2s orbital.

Periodic Table

The periodic table is a comprehensive chart that organizes elements according to their increasing atomic number, electron configurations, and recurring chemical properties. Each row on the periodic table is called a period and the elements within a period sequentially fill the orbitals. Columns are known as groups and contain elements with similar behaviors and valence electron arrangements.

Using the periodic table, one can predict the electron configuration of elements, like sodium (Na), atomic number 11. Locating sodium on the periodic table enables us to anticipate the filling of electrons up to the 3s orbital, giving Na the electron configuration: 1s² 2s² 2p⁶ 3s¹. The periodic table is an essential tool in chemistry for understanding how elements interact to form compounds.