Question

The number of protons contained in a given nucleus is called the ______

Short answer

The number of protons contained in a given nucleus is called the \(atomic number\).

Step-by-step solution

Understanding the structure of an atom

An atom consists of a nucleus at the center and electrons orbiting around it. The nucleus is made up of protons and neutrons, which are called nucleons.

Recall the characteristics of protons

Protons carry a positive charge and have a relatively large mass when compared to electrons. The number of protons in an atom determines the element's atomic number, which is used to distinguish one element from another on the periodic table.

Identify the term for the number of protons in a nucleus

The number of protons contained in a given nucleus is called the atomic number (symbolized as Z) of the element. The atomic number is the main identifier for an element, as it determines the element's chemical properties and place in the periodic table. So, the blank in the exercise should be filled with "atomic number," which refers to the number of protons in a nucleus.

Key concepts

Nucleus

The nucleus is the core of an atom, residing at its very center. It is composed of protons and neutrons, collectively called nucleons.
The nucleus is held together by strong nuclear forces, which are much more powerful than the electromagnetic forces keeping the electrons in orbit. Though small, the nucleus contains nearly all the atom's mass. This is because protons and neutrons have much more mass compared to electrons, which move in the space around the nucleus in specific energy levels or shells.

Protons

Protons are subatomic particles located inside the nucleus. They have a positive electrical charge, signified by "+1". Each proton is composed of three quarks held together by strong forces.
The number of protons in the nucleus determines the atomic number of an element, which is a unique identifier of each element on the periodic table.

• The proton's positive charge balances the negative charge of the electrons.
• The mass of a proton is approximately 1 atomic mass unit (amu), making it significantly heavier than an electron.

This balance of charge and mass is crucial for the stability of atoms.

Atomic Structure

The atomic structure refers to the arrangement of protons, neutrons, and electrons within an atom. Understanding this structure is fundamental in chemistry because it explains how atoms interact to form chemical bonds.
At the core is the nucleus, composed of protons and neutrons. Surrounding the nucleus is a cloud of negatively charged electrons in various energy levels.

• The atomic number, which is the number of protons, defines the element.
• The number of electrons usually equals the number of protons, maintaining electrical neutrality.

Different arrangements of electrons, especially in the outermost shells, influence how atoms will bond with others.

Chemical Properties

Chemical properties of an element are determined primarily by its atomic structure, particularly the electrons. The atomic number, equal to the number of protons, sets an element's place in the periodic table and indirectly affects its chemical properties.
Electrons in the outermost shell, known as valence electrons, play a critical role in chemical reactions because they are involved in forming chemical bonds with other atoms.

• Elements with the same number of valence electrons often exhibit similar chemical behaviors.
• As you move across the periodic table, changes in atomic number lead to variations in chemical properties.

This predictable pattern is related to the way electrons distribute in atom shells, guiding chemists in predicting how different elements will react with each other.