75-Archetype SyllabusChemistry • ARCH-C-01 • Spec C1

Full 6-Card Lesson 15-Question Timed Drill

UAT-UK SPEC CODE: C1 (Atomic structure)ASSUMED MATHS 1 PREREQUISITE: M6.3FREQUENCY: VERY HIGH

Subatomic Isoelectronic Ions, Isotopic A_r Weighted Means & Comma Electron Configs (Z ≤ 20)

Deconstructed from 25 past UAT-UK questions (11.11% of all historical Chemistry papers). Students using standard A-Level classroom methods spend an average of 125s on this archetype—blowing past the 90s ESAT budget. Using the 2-line Sub-90 heuristic below compresses solve time to 30s (saving 95s per question).

Historical Frequency

25 Past Qs

11.11% of Chemistry

Classroom Trap Time

125s

+35s over 90s budget

Sub-90 Target Time

30s

Banks +95s on the clock

Dominant UI Format

Table Matching

Maths 1 Skill: M6.3

Card 1 & Card 2 Preview: The Classroom Time Trap vs. Sub-90 2-Line Rule

Excerpted from our interactive 6-Step Topic Lesson for ARCH-C-01.

Launch All 6 Active-Recall Cards

CARD 1 OF 6 • THE CLASSROOM TIME TRAP (125s)

Why Students Bleed Time:

Count protons from the atomic number

Z = 7

, subtract

Z

from the mass number

A = 15

to get

15 - 7 = 8

neutrons, and add

3

electrons for the

3-

charge to get

7 + 3 = 10

electrons, filling shells as

2,8

(~95s).

In 25 past UAT-UK questions (11.11% of Chemistry), candidates lose 95s by inverting the negative charge of an electron when adjusting ion electron counts. Instead, apply C1 with Maths 1 skill M6.3.

CARD 2 OF 6 • THE 2-LINE SUB-90 HEURISTIC (<30s)

Line 1 (Charge & Shell Prune):

\text{N}^{3-}

has

7 + 3 = 10\text{ e}^- \rightarrow 2,8

(isoelectronic with

\text{Ne}

Line 2 (Neutron Check):

n = 15 - 7 = 8 \rightarrow

7 protons | 8 neutrons | 2,8 (25s).

Sanity & Limit Check: Verify units/signs against sign_or_direction_flip (Adding electrons for a positive cation M²+ (Z + 2) or subtracting electrons for an anion X²- (Z - 2)) and fence_post_or_domain_trap (Confusing neutron count (A - Z) with mass number A or proton number Z).

Examiner Distractor Blueprint for ARCH-C-01

FOIL #1sign_or_direction_flip

Adding electrons for a positive cation M²+ (Z + 2) or subtracting electrons for an anion X²- (Z - 2)

Inverting the negative charge of an electron when adjusting ion electron counts.

Open Sign / Direction Flip Clinic

FOIL #2fence_post_or_domain_trap

Confusing neutron count (A - Z) with mass number A or proton number Z

Reading nucleon number A directly as neutron number.

Open Fence-Post / Domain Trap Clinic

FOIL #3table_column_pruning_trap

Checking mass numbers before pruning rows via Group number = outer shell electron count (e.g. Group 16 = 6 outer electrons)

Not using the IUPAC Group 1-18 outer-shell shortcut to eliminate 75% of rows instantly.

Open Table Column Pruning Trap Clinic

FOIL #4intermediate_stop_trap

Solving for abundance x% of Isotope 1 when the question asks for (100 - x)% of Isotope 2

Reporting the complementary isotope percentage.

Open Intermediate Stop Trap Clinic

Try 1 Live Sample Question Under the 90-Second Stopwatch

Press W to open the 2-line dry-wipe scratchpad, select A–E, and lock in to reveal the Dual-View solution.

Full 6-Card Lesson Launch All 15 Questions (ARCH-C-01)

ARCH-C-01: Subatomic Isoelectronic Ions, Isotopic A_r Weighted Means & Comma Electron Configs (Z ≤ 20) (Sample)Chemistry

00:00.0

SUB-90 ZONE (<30S)

0.0s30s Sub-9090s ESAT Budget150s Classroom

Question 1 of 1ARCH-C-01 (6-Card Lesson)Format: Standard 5-Option

Right-click any option to cross out • Keys A–E + Enter

Question 1 of 1 • 90s Target

Ready to Start Question 1?

The question stem, diagram, and answer options are hidden behind this pre-start gate. When you click below, the question will reveal and your 90-second split stopwatch will immediately begin ticking.

Chemistry•ARCH-C-01•Standard 5-Option

or press Enter to start