Problem 41 How many orbitals are completely... [FREE SOLUTION]

Chapter 3: Problem 41

How many orbitals are completely filled in an atom of an element whose atomic number is 18?

Short Answer

Expert verified

There are 5 completely filled orbitals in an atom of an element whose atomic number is 18.

Step by step solution

Understanding atomic structure

In an atom, electrons are contained in space called orbitals. Each orbital can hold up to two electrons. The orbitals are filled according to the following sequence: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p and so on.

Applying electron filling rule

Elementary atomic number 18 means this atom has 18 electrons. The filling sequence would be: \n1s^2 (2 electrons), 2s^2 (2 electrons), 2p^6 (6 electrons), 3s^2 (2 electrons), 3p^6 (6 electrons).\nAdding these up we get a total of 18 electrons, which matches with the atomic number of the given element.

Counting completely filled orbitals

According to the filling sequence, the completely filled orbitals are: 1s, 2s, 2p, 3s and 3p. That's a total of 5 orbitals.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Atomic Structure

Atoms are the fundamental building blocks of matter. They are incredibly small, composed of even smaller particles called protons, neutrons, and electrons. At the center of an atom is the nucleus, which contains protons and neutrons. Surrounding the nucleus is a cloud of electrons that occupy regions known as orbitals.

Protons: Positively charged particles found in the nucleus.
Neutrons: Neutral particles, also in the nucleus, with no charge.
Electrons: Negatively charged particles that orbit the nucleus.

Electrons are organized in energy levels or shells, which are further divided into orbitals. Each orbital can hold up to two electrons. The structure of an atom, especially the arrangement of electrons, determines its chemical properties and reactivity.

Orbital Filling Sequence

The order in which electrons occupy orbitals is governed by a set of rules known as the filling order or sequence. This sequence is determined by the increasing energy levels of the orbitals.
Orbital filling follows the "Aufbau Principle," which means electrons fill the lowest energy orbitals first before moving to higher ones. The sequence often taught is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on. The key principles guiding this order are:

Pauli Exclusion Principle: Each orbital can hold a maximum of two electrons with opposite spins.
Hund's Rule: Electrons will fill an unoccupied orbital before they pair up in an occupied one.

Understanding this sequence is crucial as it helps predict and explain the chemical behavior of elements.

Atomic Number

The atomic number of an element is one of its defining characteristics. It tells us the number of protons in the atom鈥檚 nucleus, and correspondingly, the number of electrons in a neutral atom.
For example, an element with an atomic number of 18 has 18 protons and, in a neutral state, 18 electrons. This atomic number is unique to each element and helps in identifying them on the periodic table. The importance of knowing the atomic number:

It determines the position of an element on the periodic table.
It reveals the electronic configuration of the element.
It helps in predicting the chemical behavior of the element.

By understanding the atomic number, you can better grasp how elements interact and combine to form compounds.

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How many orbitals are completely filled in an atom of an element whose atomic number is 18?

Short Answer

Step by step solution

Understanding atomic structure

Applying electron filling rule

Counting completely filled orbitals

Key Concepts

Atomic Structure

Orbital Filling Sequence

Atomic Number

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