Question

Zinc A zinc atom contains a total of 18 electrons in its 3s, 3p, and 3d orbitals. Why does its electron-dot structure show only two dots?

Short answer

The electron-dot structure of a zinc atom shows only two dots because zinc has two valence electrons in its 4s orbital. The electron configuration of zinc is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰, and the valence electrons are located in the outermost energy level (the 4th energy level). Thus, the two dots in the electron-dot structure represent the two valence electrons in the 4s orbital.

Step-by-step solution

Identify the atomic number of zinc

Look up the atomic number of zinc on the periodic table. The atomic number reflects the number of protons in the nucleus and also the number of electrons in a neutral atom. In the case of zinc, the atomic number is 30. This means that a zinc atom has 30 electrons.

Determine the electron configuration of zinc

To write the electron configuration of zinc, we follow the rules of Aufbau principle, Pauli exclusion principle, and Hund's rule. The electron configuration of zinc is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰.

Identify the valence electrons

The valence electrons are located in the outermost energy level of an atom. In the case of zinc, the outermost energy level is the 4th energy level. The electron configuration shows that there are two electrons in the 4s orbital: 4s². Hence, zinc has two valence electrons.

Draw the electron-dot structure

The electron-dot structure represents the valence electrons as dots surrounding the chemical symbol of an element. For zinc, we will have two dots around the symbol "Zn" to represent its two valence electrons. The electron-dot structure of zinc is: . Zn . . In conclusion, the electron-dot structure of a zinc atom shows only two dots because zinc has two valence electrons in its 4s orbital.

Key concepts

Valence electrons

Valence electrons are the outermost electrons of an atom. They play a key role in chemical bonding and reactions. These electrons are located in the highest energy level of an atom and are crucial in determining an element's chemical properties.
A simple way to locate the valence electrons is by looking at the atom's electron configuration. For example, zinc has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰. Among these, the electrons in the 4s sublevel are the furthest out and make up the valence electrons for zinc.
Understanding which electrons are valence allows prediction of how atoms interact with others. For zinc, with two valence electrons, it's able to form certain bonds easily but might not form others as readily.

Electron-dot structure

The electron-dot structure is a simple yet powerful way to visualize an atom's valence electrons. Also known as Lewis dot diagrams, these structures use dots around an element's symbol to represent valence electrons, which helps predict how the element might bond with others.
For zinc, which has two valence electrons, the electron-dot structure is represented by placing two dots around the chemical symbol "Zn". These dots provide insight into potential bonding patterns and reactivity. Specifically, zinc's configuration implies that it can form two bonds, by potentially giving away its two electrons during chemical reactions or interactions.

Periodic table

The periodic table is a comprehensive map of the known elements, arranged in a way that showcases periodic trends of elemental properties. Each element is placed in a specific position based on its atomic number, which corresponds to the number of protons and electrons in a neutral atom.
This organization is not only about listing elements but also about revealing patterns. For instance, elements in the same group (vertical columns) often have similar valence electron arrangements, which gives them related chemical properties. Zinc, found in group 12, has a unique combination of filled and partially filled sublevels that influence its placement and chemical behavior.
The table is instrumental for quickly determining important characteristics of an element, like oxidation states, common bonding partners, and typical compounds formed.

Electron configuration rules

Electron configurations are guided by a set of rules that dictate how electrons are distributed in an atom. These rules include the Aufbau principle, the Pauli exclusion principle, and Hund's rule.
The Aufbau principle tells us that electrons fill atomic orbitals starting from the lowest energy level to the highest. This is akin to filling seats from the front of a bus to the back.
The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers. Essentially, an orbital can hold a maximum of two electrons, with opposite spins.
Hund’s rule indicates that electrons will fill an unoccupied orbital before they pair up in an occupied one, much like preferring your own seat before sharing. These principles ensure an orderly and predictable filling of electron shells.
These rules are reflected in zinc’s electron configuration, as seen in its distribution: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰. It reflects systematic filling from lower to higher energy levels, achieving stability through full sublevels.