Problem 54 - Chemistry Matter and Change

Question

Fireworks Barium is a metal that gives a green color to fireworks. Write the electron configuration for barium. Classify it according to group, period, and block in the periodic table

Step-by-Step Solution

Answer

The electron configuration of barium (Ba) is \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2\). It is classified as belonging to Group 2 (alkaline earth metals), Period 6, and the 's' block in the periodic table.

Step 1: Write the electron configuration of barium

To write the electron configuration of barium, we will follow the order in which electrons fill up the orbitals in an atom. With an atomic number of 56, barium has 56 electrons. The electron filling order is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f Following this order, the atom fills up its orbitals with 2 electrons in the s-orbitals, 6 electrons in the p-orbitals, 10 electrons in the d-orbitals, and 14 electrons in the f-orbitals. The electron configuration for barium is: \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2\)

Step 2: Determine barium's group, period, and block

Refer to the periodic table to find barium's position: - Group: Barium is located in Group 2, also known as the alkaline earth metals. - Period: Barium is found in Period 6. - Block: Barium is in the 's' block, as the last electron enters the 6s orbital. So, barium belongs to Group 2, Period 6, and 's' block of the periodic table.

Key Concepts

Understanding the Periodic Table

At the very heart of chemistry lies the periodic table, a tabular display that organizes all the known elements according to their chemical properties. It serves as a roadmap for understanding how elements behave and interact with each other. Elements in the periodic table are arranged in rows (periods) and columns (groups or families) based on their atomic number — the number of protons in the nucleus of an atom.

Each period on the table corresponds to a higher energy level occupied by the electrons of an atom. The table also divides elements into blocks— 's', 'p', 'd', and 'f'—which are based on the atomic orbitals that the electrons fill last. The 's' block includes the first two groups, the 'p' block contains Groups 13 through 18, the 'd' block spans Groups 3 through 12, and the 'f' block, which includes the lanthanides and actinides, is placed separately at the bottom of the table. Understanding this layout is crucial when determining the electronic configuration of an element like barium, as well as its placement within a specific period, group, and block.

Diving into Alkaline Earth Metals

Alkaline earth metals are renowned for their higher electrical conductivity and lustrous, silvery-white appearance. Nestled in Group 2 of the periodic table, these metals include beryllium, magnesium, calcium, strontium, barium, and radium. They are considered 'alkaline' because their aqueous solutions are basic (alkaline) and 'earth' because they were first isolated from minerals found in the Earth's crust.

These metals display certain characteristic properties, such as being relatively soft and having low densities and melting points compared to transition metals. Alkaline earth metals readily lose their two outermost electrons to achieve a stable electron configuration, forming the +2 oxidation state, which accounts for their high reactivity, especially with water. Barium, for instance, imparts a distinctive green color to fireworks and adheres to this typical +2 oxidation state common to its group.

Atomic Orbitals and Electron Configuration

Atomic orbitals are regions around an atom's nucleus where electrons are likely to be found most of the time. These orbitals come in several shapes, such as spherical ('s'), dumbbell ('p'), cloverleaf ('d'), and complex ('f'). The arrangement of electrons within these orbitals constitutes the electron configuration of an element, which is pivotal in understanding an element's chemical behavior.

The electron configuration is determined by principles such as the Aufbau principle (which postulates that electrons fill up orbitals starting at the lowest available energy level), Hund's rule (stating that electrons will fill an unoccupied orbital before they pair up), and the Pauli Exclusion Principle (indicating that no two electrons can have the same set of all four quantum numbers). For an element like barium, the electron filling order signifies how these principles guide the distribution of electrons into the 's', 'p', 'd', and 'f' orbitals, culminating in the noted electron configuration of \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 \). This configuration dictates the chemical and physical properties of barium, including its characteristic emission of green light in fireworks.