Atomic Number and Mass Number Quiz

Atomic Number

• Defined by the number of protons present in the nucleus of an atom
• Represents the identity of an element
• Unique to each element

Subatomic Particles

• Protons: have a positive charge, located in the nucleus, and determine the atomic number
• Neutrons: have no charge, located in the nucleus, and contribute to the mass number
• Electrons: have a negative charge, located outside the nucleus, and have negligible mass

Mass Number

• Defined by the sum of protons and neutrons in an atom
• Represents the total number of nucleons in an atom
• Can vary for the same element, resulting in different isotopes

Atomic Number in the Periodic Table

• Represented by the symbol Z
• Placed at the top of each element's box in the periodic table

Calculating Neutrons

• Number of neutrons = Mass Number - Atomic Number
• Requires knowledge of both atomic and mass numbers

Importance of Atomic Number

• Considered a fundamental property of an element
• Determines the chemical properties of an element

Mass Number vs. Atomic Mass

• Mass number is an integer value, while atomic mass is a weighted average of the mass numbers of naturally occurring isotopes

Isobars

• Atoms of different elements with the same mass number
• Distinguished by their atomic numbers

Neutrons

• Have no charge
• Located in the nucleus
• Contribute to the mass number of an atom

Determining Atomic Number

• Can be determined by the number of protons in an atom
• Unique to each element

Mass Number and Isotopes

• Isotopes of an element have the same atomic number but different mass numbers
• Result from variations in the number of neutrons

Calculating Mass Number

• Mass Number = Number of Protons + Number of Neutrons

Importance of Neutrons

• Must know the number of neutrons to find the mass number of a specific atom