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Difficulty: MediumAtomic Structure and Periodic Table

Match each fundamental atomic structure concept with its correct scientific definition.

  • Atomic numberThe quantity of protons in an atomic nucleus that uniquely establishes elemental identity
  • Mass numberThe total sum of protons and neutrons contained inside an atom's nucleus
  • IsotopesAtoms of the same element possessing identical proton numbers but differing numbers of neutrons
  • Valence electronsElectrons occupying the outermost energy level that primarily dictate chemical reactivity and bonding

Answer

Atomic number pairs with the proton quantity determining elemental identity; Mass number pairs with the sum of protons and neutrons; Isotopes pair with atoms having identical protons but different neutrons; Valence electrons pair with outermost electrons governing chemical reactivity.
Each term accurately describes a foundational property of atomic architecture: the atomic number corresponds strictly to proton count, mass number equals protons plus neutrons, isotopes are variants differing in neutron count, and valence electrons occupy the outermost shell to drive chemical behavior.

Step-by-Step Solution

1
Identify the definition of atomic number
Matched with the number of protons that defines the element (ZZ)
Every neutral or ionized atom of an element always contains the same characteristic number of protons.
2
Identify the definition of mass number
Matched with the sum of nuclear particles (protons + neutrons)
Electrons have negligible mass compared to nucleons, so atomic mass number is the total count of protons and neutrons.
3
Identify the definition of isotopes
Matched with atoms of the same element containing differing neutron quantities
Because atomic number remains constant for a given element, variations in atomic mass within an element arise solely from neutron count.
4
Identify the definition of valence electrons
Matched with the outermost electrons governing bonding behavior
The electron configuration in the highest energy level dictates how an atom interacts and shares or transfers electrons during reactions.

Key Concept

Core atomic structure parameters, subatomic particle arrangements, and isotopic terminology
Estimated Time:1m 0s
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Topics

Atomic Structure and Periodic Table

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