Atomic Structure and Isotopes

Isotopes

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. This difference in neutron number results in different mass numbers for isotopes of the same element.

• Atomic Number (Z): The number of protons in the nucleus of an atom. It determines the chemical properties and identity of the element.

• Mass Number (A): The total number of protons and neutrons in the nucleus.

• Neutrons (n): Calculated as the difference between the mass number and atomic number.

• Electrons (e-): In a neutral atom, the number of electrons equals the number of protons.

Example: For Calcium-43 (Ca):

• Protons: 20

• Neutrons:

• Electrons: 20 (neutral atom)

Atomic View

The atomic view summarizes the relationships between subatomic particles in an atom:

• Number of neutrons (n):

• Mass Number (A):

• Number of protons (p+):

• Atomic Number (Z): Number of protons

• Number of electrons (e-): (for neutral atoms)

• Element Identity: Determined by the number of protons

Isotope Notation

Isotope notation includes the atomic number (Z), mass number (A), and element symbol (X):

• General form: X

• A: Mass number (protons + neutrons)

• Z: Atomic number (protons)

• X: Element symbol

Practice Questions and Examples

Example: Calcium-43 Isotope

Given: Mass number = 43, Atomic number = 20

• Protons: 20

• Neutrons:

• Electrons: 20

Correct answer: 20 protons, 23 neutrons, and 20 electrons

Practice: Strontium-88 (Sr)

• Protons: 38

• Neutrons:

• Electrons: 38

Correct answer: 38 protons, 50 neutrons, and 38 electrons

Practice: Sulfur-34 (S)

• Protons: 16

• Neutrons:

• Electrons: 16

Correct answer: 16 protons, 18 neutrons, and 16 electrons

Tabular Comparison of Isotopes

The following table summarizes the subatomic particles for several isotopes:

Additional info: The entries labeled "amina-75" appear to be placeholders or possibly typographical errors. In a standard chemistry context, isotopes are named by their element and mass number (e.g., Aluminum-27). The table demonstrates how to calculate neutrons: .

Summary of Key Equations

• (for neutral atoms)