Chemistry: Atomic Structure, Ions, Isotopes, Valence Electrons, Bonds, & Periodic Table

What are the three subatomic particles, their locations, electrical charges, and approximate masses in atomic mass units (amu)?

• Protons: Located in the nucleus; charge = +1 (P for Positive); mass ~ 1 amu.

• Neutrons: Located in the nucleus; charge = 0 (N for Neutral); mass ~ 1 amu

• Electrons: Orbit around the nucleus in rapid motion; charge = -1; mass is negligible (~ 0.000549 amu) and omitted from atomic mass calculations.

What does the PAN MAN mnemonic stand for when reading the periodic table?

• PAN: Protons = Atomic Number

• MAN: Mass number - Atomic number = Neutron (Mass - Atomic # = Neutrons)

What is an Isotope, and what determines an element’s chemical identity?

• Isotopes: Atoms of the same elements with the same number of protons but a different number of neutrons (and thus different mass numbers).

• Identity: The number of protons (atomic number) strictly defines the element (e.g., Carbon-12, 13, and 14 all contains exactly 6 protons).

What is the difference between Cation and Anion? Includes Nurse Cheung’s mnemonics.

• Cation: A positively charges ion formed when an atom loses electrons (Mnemonic: “Cat-ion has PAWS”/positive; e.g., Na⁺ has 11 protons, 10 electrons).

• Anion: A negatively charged ion formed when an atom gains electrons (Mnemonic: “A Negative Onion”; e.g., O^2- has 8 protons, 10 electrons).

What are the 4 main electron shells (n), their letters, and the subshells present in each?

• n = 1 (K shell): s subshell

• n = 2 (L shell): s, p subshells

• n = 3 (M shell): s, p, d subshells

• n = 4 (N shell): s, p, d, f subshells

How many maximum electrons can each subshells (s, p, d, f) hold, and what are their characteristic shapes?

• s subshell: Max 2 electrons; spherical / circular shape

• p subshell: Max 6 electrons; dumbbell shape

• d subshell: Max 10 electrons; four-leaf clover shape

• f subshell: Max 14 electrons; complex multi-lobed shape

• (Pattern: Each progressive subshell adds 4 electrons: 2 → 6 → 10 → 14)

What is the maximum number of electrons that can occupy each principal energy level/shell (n = 1, 2, 3, 4)?

• n = 1: 2 electrons (2)

• n = 2: 8 electrons (2 + 6)

• n = 3: 18 electrons (2 + 6 + 10)

• n = 4: 32 electrons (2 + 6 + 10 + 14)

What is the Octet Rule, and which electrons participate in bonding?

• Valence Electrons: Only electrons in the outermost shell participate in chemical bonding.

• Octet Rule: Atoms gain, lose, or share electrons to achieve a stable configuration of 8 valence electrons (Exceptions include Hydrogen and Helium, which are stable with 2 electrons in the n = 1 shell).

What define and Ionic Bond, and what is Nurse Cheung’s mnemonic?

• Mechanism: Chemical bond formed by the transfer (donation and acceptance) of electrons between atoms, creating oppositely charged ions that attract (e.g., Na⁺ and Cl^- forming NaCl).

• Mnemonic: “I take, you give”

What defines a Covalent Bond, and what is Nurse Cheung’s mnemonic?

• Mechanism: Chemical bond formed when two atoms share one or more pairs of electrons to complete their outer shells (common among nonmetals like C, H, O, N; e.g., double bonds in CO₂).

• Mnemonic: “Covalent = Caring/Sharing is caring”.

What do Periods (horizontal rows) represent on the Periodic Table?

• The 7 horizontal rows are the Periods.

• The period number indicates the total number of electron shells (energy levels) an element possess (e.g., Period 2 elements have 2 shells; Period 6 elements have 6 shells).

What do Groups (vertical columns) represent on the Periodic Table, and how do they correlate with valence electrons?

• The vertical columns are Groups/Families; elements in the same group share similar chemical properties.

• For main-group elements (Groups 1A-8A), the group number matches the number of valence electrons (e.g., Group 2A elements have 2 valence electrons; Group 7A halogens have 7 valence electrons).