Review 2026 | Study Guide,
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Updated 2026 Questions and Answers
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Rationales
Included
, average atomic mass weighted average of all of the isotope's mass numbers found in nature
valence electrons electrons in the outermost shell (can be easily shared, gained or lost)
core electrons electrons in the inner shell
Pauli Exclusion Principle An atomic orbital may describe at most two electrons, each with opposite spin
direction
Hund's Rule electrons do not pair up until they have to
Aufbau Principle An electron occupies the lowest-energy orbital that can receive it
lewis Structures
Nobel Gas Notation shortcut→ find the closest noble gas (column 18) with fewer electrons than the
element then finish electron configuration
transition elements What are the elements in groups 3-12 called?
electronegativity A measure of the ability of an atom in a chemical compound to attract electrons
ionization energy The amount of energy required to remove an electron from an atom
alpha decay A nuclear reaction in which an atom emits a ________ particle consisting of two
protons and two neutrons. This decreases the atomic number by 2 and the mass
number by 4.