High Yield Chemistry IMAT

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What a mass spectrum does not tell you?

Electron configurations or chemical reactivity (those depend on the atomic number Z, the same for all isotopes of an element).; How protons and neutrons are arranged inside the nucleus (mass spectrometry separates whole ions by total mass only).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What an “orbital” really means?

n (principal): shell or energy level – 1, 2, 3 …; l (angular): sub‑level – 0 =s, 1 =p, 2 =d, 3 =f

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Atomic Absorption and Emission Line Spectra (71)?

Lines correspond to nhigh → nlow with nlow = 2 (visible light).; Wavelengths: H‑α = 656 nm (red) • H‑β = 486 nm (cyan) • H‑γ = 434 nm (violet) • H‑δ = 410 nm.; Convergence at the violet end proves that energy levels get closer together as n increases – exactly what the Bohr model predicts.; Answer 1: number of wave crests passing a point per second (Hz).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Atomic Orbitals (76)?

n (principal): shell or energy level – 1, 2, 3 …; l (angular): sub‑level – 0 =s, 1 =p, 2 =d, 3 =f; Memorise s‑ and p‑shapes – spheres vs dumb‑bells appear in IMAT diagrams.; Practice turning a given configuration into a Periodic‑Table position (use the blocks – s 2 wide, p 6, d 10).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Atomic Structure (58)?

~0.01 % were deflected through 90° – “like a shell rebounding from tissue paper.”; 400 BCE – 1800 — Stoichiometric fixed ratios (Proust) — Hard, indivisible “Dalton” spheres; 1897 — Cathode rays & charge‑to‑mass ratio (J. J. Thomson) — “Plum‑pudding” – electrons in a diffuse + charge; 1909 / 1911 — Alpha‑particle scattering (Geiger–Marsden/Rutherford) — Nuclear atom – dense + nucleus; electrons outside

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Aufbau Principle: Orbital Diagrams (79)?

1 orbital in each s → 2 e⁻; 3 orbitals in each p → 6 e⁻; 5 orbitals in each d → 10 e⁻; 7 orbitals in each f → 14 e⁻

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Electron spin and the Pauli Exclusion Principle (78)?

→ One orbital can hold max 2 electrons, and they must have opposite spins.; → Sets the overall capacity rules: s = 2 e–, p = 6, d = 10, f = 14.; 4s vs 3d order changes after ionisation → always remove 4s first.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Evidence for the Bohr model (72)?

Lines converge toward 364 nm (the series limit). — Levels crowd closer together as n increases; the limit is reached when n → ∞ (ionisation).; The ionisation energy of H is 2.18 × 10−18 J. — Bohr’s highest jump (n = ∞ → 1) gives exactly that energy difference (E1 = −2.18 × 10−18 J).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Ions (64)?

Cation – positive ion. Formed when the atom loses one or more electrons (protons electrons).; Anion – negative ion. Formed when the atom gains electrons (electrons protons).; A = 19 + 20 = 39 → 3919K; Net charge: 19 − 18 = +1 → 3919K+

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Isotopes (63)?

Chemical reactivity, bonding, colour … — None. Electrons set chemistry and every isotope has the same electronconfiguration.; Mass‑dependent properties (b.p., m.p., diffusion rate) — Slight shift. Extra neutrons → heavier, so e.g. 37Cl2 diffuses ≈3 % more slowly than 35Cl2.; Nuclear stability / radioactivity — Big change. Some N : Z ratios are unstable → β‑, α‑ or γ‑decay.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Mass Spectra (67)?

x‑axis → m / z (mass‑to‑charge ratio). With singly‑charged ions (z = +1) the value is the isotope’s mass number A.; y‑axis → % abundance. The detector counts how often each peak appears and scales the tallest one to 100 % (or another convenient maximum such as 80 %).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Schrödinger Model of The Hydrogen Atom (75)?

l = 0 → (n‑1) sub‑level: s (l=0), p (1), d (2), f (3); ms = ± ½ electron spin – max two electrons per orbital, opposite spins

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about The Electromagnetic Spectrum (69)?

Each level splits into sub‑levels in the order: s, p, d, f.; Cr (Z = 24) – takes the half‑filled d: [Ar] 4s1 3d5.; Cu (Z = 29) – full d: [Ar] 4s1 3d10.; Fe3+ (from Fe: [Ar] 4s2 3d6) → lose 4s2 and one 3d → [Ar] 3d5.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are high-yield facts to remember about Wave and Particle Models (74)?

Electron diffraction (Davisson‑Germer, 1927). A beam of electrons passing through a thin Ni crystal produced concentric rings – the hallmark of waves interfering.; Photon or electron energy gap: ΔE = h ν = h c / λ; de Broglie wavelength: λ = h / p = h / (m v); Uncertainty relationship: Δx Δp ≥ ħ/2, with ħ = h / (2π)

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about 2.5 Nuclear symbol notation AZX?

Z = atomic number = protons = electrons in neutral atom.; A = mass number = protons + neutrons.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about 3 Energy levels, shells and sub‑levels?

Main energy level (n) can hold 2n2 electrons in total.; An s orbital holds 2 e‑; a set of three p orbitals holds 6; five d orbitals hold 10; seven f orbitals hold 14.; Orbitals are regions of high probability, not little circular orbits.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Electron capacities you must know once and forever?

1 orbital in each s → 2 e⁻; 3 orbitals in each p → 6 e⁻; 5 orbitals in each d → 10 e⁻; 7 orbitals in each f → 14 e⁻

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about From principal levels (n) to sub‑levels (s p d f)?

s – 1 orbital → 2 e–; p – 3 orbitals → 6 e–; d – 5 orbitals → 10 e–; f – 7 orbitals → 14 e–

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Isotopes – same Z, different mass?

All isotopes of chlorine have 17 protons (so Z=17).; The common pair are 35Cl (N=18) and 37Cl (N=20).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Key equations?

En = −k / n2 (k = 2.18 × 10−18 J); ΔE = h ν = h c / λ; 1/λ = RH(1/nlower2 − 1/nupper2)

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Key take‑aways for IMAT / chem MCQs?

Pauli exclusion sets the “2 per orbital” rule.; Electron spin is the reason two electrons can share the same 3‑D region.; 4s vs 3d order changes after ionisation → always remove 4s first.; Unpaired spins = paramagnetic; all paired = diamagnetic.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Positive ions (cations)?

Aluminium example; Transition‑metal twist

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Quick orbital‑count checklist?

Each shell n holds 2 n² electrons in total.; Total orbitals per shell = n².; Maximum electrons in a sub‑level = 2 (2l + 1).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Sub‑level capacities – memorize once?

Orbitals in sub‑level = 2 l + 1 ⇒ s (0)=1, p (1)=3, d (2)=5, f (3)=7; Electrons per orbital = 2 (Pauli) ⇒ capacities \2, 6, 10, 14\; Total electrons per shell = 2 n² (gives 2 8 18 32 …)

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about Take‑away toolbox?

Write a neat “100‑atoms” table → multiply → divide by 100.; For diatomics, enumerate all isotope pairs first.; Rutherford nailed the nuclear atom; Bohr nailed the energy levels.

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about What a mass spectrum does not tell you?

Electron configurations or chemical reactivity (those depend on the atomic number Z, the same for all isotopes of an element).; How protons and neutrons are arranged inside the nucleus (mass spectrometry separates whole ions by total mass only).

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] What are key points about 📌Difference Between Isomers and Isotopes?

Types of Isomers; Importance; Types of Isotopes; Characteristics

[CHEM][ATOMIC-STRUCTURE][HIGH-YIELD] Where do the numbers come from? — The mass spectrometer?

Ionise the sample (e.g. M → M+ + e⁻).; Accelerate the ions through an electric field so they all gain the same kinetic energy.; Deflect them in a magnetic field; lighter (smaller m/z) ions bend more.; Detect the ions separated by their m/z ratio. Peak height ↔ relative abundance of that isotope.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] How a mass spectrum is plotted?

x‑axis → m / z (mass‑to‑charge ratio). With singly‑charged ions (z = +1) the value is the isotope’s mass number A.; y‑axis → % abundance. The detector counts how often each peak appears and scales the tallest one to 100 % (or another convenient maximum such as 80 %).

[CHEM][ATOMIC-STRUCTURE][APPLICATION] How to build (or strip) an ion’s configuration?

Electrons are removed from / added to the highest‑energy sub‑level(s) first.; Remove electrons from the outermost sub‑level(s) – check the n value.; Aluminium example; Transition‑metal twist

[CHEM][ATOMIC-STRUCTURE][APPLICATION] How to draw orbital boxes in the exam?

Write the sub‑level label under each box (e.g. 2p).; Add one box per orbital (2p → three boxes).; Fill with half‑arrows ↑ following Aufbau, Hund, Pauli.; Pair with ↓ only after every box has one ↑.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] How to visualise the link?

Absorption spectra of chlorophylls show sharp peaks – direct evidence that those molecular energy gaps are discrete, just as Bohr predicted for atomic hydrogen.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] Why 2 n² appears so often?

Combine the formula “ of orbitals = n²” (from quantum mechanics) with “2 electrons per orbital” → shell capacity = 2 n². The same expression appears when you are asked for the maximum number of electrons that fit into all sub‑levels with principal quantum number ≤ n.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] Why Bohr’s neat orbits were not enough?

Experimental clues forced physicists to rethink; Photoelectric effect. Only photons above a threshold frequency eject electrons, as if light arrives in discrete energy packets (Einstein’s “photons”).; Line spectra of multi‑electron atoms. Relative intensities & positions could not be matched by a single‑orbit picture.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] Why chemists care?

Periodic trends. Ionisation energy, atomic radius, and electronegativity follow directly from how tightly each orbital holds its electron density.; Spectroscopy. UV‑visible, IR, and NMR techniques all probe transitions between quantised energy levels predicted by the wave model.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] Why Cr and Cu break the pattern?

Exchange energy & symmetry – half‑filled (d5) or filled (d10) sets maximise parallel spins and orbital symmetry, lowering total repulsion.; Spectroscopic proof – experimental spectra & photo‑electron data match the “promoted” configurations; 4s electrons ionise first in Cr and Cu.

[CHEM][ATOMIC-STRUCTURE][APPLICATION] Why the fractional mass in the Periodic Table?

The printed value under “Cl” (35.45) is the weighted mean of all chlorine atoms in nature Ar(Cl)=(0.775×35)+(0.225×37)1=35.45Ar​(Cl)=1(0.775×35)+(0.225×37)​=35.45

[CHEM][ATOMIC-STRUCTURE][COMPARE] What should you know about 400 BCE – 1800 in 2 The Atom – why structure matters?

Stoichiometric fixed ratios (Proust); Hard, indivisible “Dalton” spheres

[CHEM][ATOMIC-STRUCTURE][RECALL] What is an anion?

A negatively charged ion formed when an atom gains one or more electrons.

[CHEM][ATOMIC-STRUCTURE][RECALL] What is the de Broglie wavelength relationship?

λ = h/p = h/(mv).

[CHEM][ATOMIC-STRUCTURE][RECALL] What are geometric (cis-trans) isomers?

Isomers that differ in spatial arrangement around a double bond or ring because rotation is restricted.

[CHEM][ATOMIC-STRUCTURE][RECALL] What does atomic number Z represent?

The number of protons in the nucleus; it identifies the element.

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Covalent Bonding (148)?

Single bond (σ) – one shared pair • H‑H, H‑Cl, C‑H; Double bond (σ + π) – two shared pairs • O=O, C=O; Triple bond (σ + 2π) – three shared pairs • N≡N, C≡C; Bonding (shared) pair: electrons engaged in σ/π bonding; density concentrated between nuclei.

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Hybridization in Molecules With Expanded Octets (203)?

2 — linear — CO2 — sp; 3 — planar triangular — BCl3 — sp2; 3 — planar triangular → V‑shaped — SO2 — sp2; 4 — tetrahedral — CH4 — sp3

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Intermolecular Forces (173)?

Electron count ↑ → dispersion ↑ → boiling point ↑; Chain length ↑ / branching ↓ → surface area ↑ → dispersion ↑; Non‑polar & small (He, N2, CH4) → London dispersion only.; Non‑polar but large (I2, hexane) → Dispersion still only IMF, yet significantly stronger.

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Lewis Structure (156)?

CH4 — 8 — H‑C‑H (four single bonds; no lone pairs); NH3 — 8 — three N‑H bonds & one lone pair on N; H2O — 8 — two O‑H bonds & two lone pairs on O; CO2 — 16 — O=C=O (each O with two lone pairs)

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Metallic Bonding (181)?

Brass = Cu + Zn → increased hardness, used in musical instruments & fittings.; Bronze = Cu + Sn → corrosion‑resistant statues, bearings.; Steel = Fe + C (+ other elements) → huge range of strengths and uses.; Na — 1 — Na+ — 98

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Ozone (193)?

Ozone’s Lewis depiction requires two equivalent resonance forms: O=O–O ↔ O–O=O; Because the π electrons are delocalised over both O–O positions, the bond order is 1.5 and each O–O bond length lies between a single and a double bond.; absorbs harmful ultraviolet radiation (≈ 100 – 330 nm)

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Sigma and Pi (198)?

s + s (e.g. H–H in H2); s + p (e.g. H–F in HF); p + p (end‑on, e.g. F–F in F2); Orbital alignment — end‑on, along axis — side‑on, parallel p

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about SP Hybridization (202)?

1 C–C σ bond (sp–sp overlap); 2 C–H σ bonds (sp–s overlap); Remaining two p orbitals on each C overlap sideways twice → 2 π bonds.; Electron‑domain geometry: linear (180°).

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about SP2 Hybridization (202)?

The leftover p orbital on each sp² atom can overlap sideways → one π bond.; Each C is sp²‑hybridized → three C–H/C–C σ bonds (coplanar).; Unhybridized p orbitals overlap → one C=C π bond (electron density above & below plane).; 0 lone pairs — trigonal planar 120° (e.g. ethene C2H4)

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about SP3 Hybridization (201)?

Orientation: corners of a tetrahedron.; Ideal angle: 109.5°.; C is sp³‑hybridized → four identical C–H σ bonds.; All H–C–H angles = 109.5°, explaining the observed symmetry.

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Species With Four Electron Domains (161)?

4 bonding, 0 lone → tetrahedral 109.5°; 3 bonding, 1 lone → trigonal‑pyramidal ≈ 107°; 2 bonding, 2 lone → bent ≈ 105°

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Species With Six Electron Domains (187)?

Because all six positions are equivalent, lone pairs occupy any site without creating axial–equatorial distinctions.; 6 : 0 — Octahedral — 90° — SF6; 5 : 1 — Square pyramidal — < 90° — BrF5; 4 : 2 — Square planar — 90° — XeF4

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about Species With Two or Three Electron Domains (160)?

2 domains → linear (180°); 3 domains → trigonal‑planar “umbrella” (120°); O=C=O — central C has two regions of electron density (each double bond counts once) — linear, bond angle 180°; H‑C≡C‑H — central C (in bold) H‑C≡C‑H – only 2 domains around the bold carbon — linear, 180°

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about The Sigma (σ) Bond (198)?

Orbital alignment — End‑on overlap along the bond axis; Electron density — Concentrated between the two nuclei; Presence in molecules — Every single bond; first bond in double/triple bonds; Rotational freedom — Free rotation about the bond axis (unless restricted by the surrounding geometry)

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about 📌Easy Steps for Drawing Lewis Structures and Common Exceptions?

Boron (B): Often forms compounds like BF3 with only 6 electrons around boron.; Beryllium (Be): Typically forms compounds like BeCl2 with only 4 electrons around beryllium.; Phosphorus (P): Can have up to 10 electrons (e.g., PCl5).; Sulfur (S): Can have up to 12 electrons (e.g., SF6).

[CHEM][BONDING][HIGH-YIELD] What are high-yield facts to remember about 📌Sequence of Bond Strength from Non-Polar to Ionic?

Nature: Weak, temporary dipoles induced in atoms or molecules.; Strength: Weakest type of intermolecular force.; Nature: Electrostatic attractions between the positive end of one polar molecule and the negative end of another.; Strength: Stronger than van der Waals forces but weaker than hydrogen bonds.

[CHEM][BONDING][HIGH-YIELD] What are key points about 1 · From neutral atoms to charged ions?

Metals (Groups 1, 2, 13) have only a few valence electrons; losing them is energetically easiest ➝ cations.; Non‑metals (Groups 15, 16, 17) are close to a filled shell; gaining electrons is favoured ➝ anions.

[CHEM][BONDING][HIGH-YIELD] What are key points about 2 · Electrostatic attraction = the ionic bond?

higher ionic charges (MgO NaCl), and; smaller ionic radii (LiF CsI).

[CHEM][BONDING][HIGH-YIELD] What are key points about 2 • Factors affecting bond strength?

Number of delocalised electrons per atom (e.g. Mg supplies 2 e⁻ while Na supplies 1 e⁻).; Charge on the cation (higher charge ⇒ stronger attraction).; Ionic radius (smaller cation ⇒ electrons are closer ⇒ attraction increases).

[CHEM][BONDING][HIGH-YIELD] What are key points about 4 • Alloys – tuning metallic properties?

Brass = Cu + Zn → increased hardness, used in musical instruments & fittings.; Bronze = Cu + Sn → corrosion‑resistant statues, bearings.; Steel = Fe + C (+ other elements) → huge range of strengths and uses.

[CHEM][BONDING][HIGH-YIELD] What are key points about Bond order in a resonance hybrid?

Bond order = (number of π bonds shared between the same two atoms) / (number of equivalent positions) + 1 for the σ‑bond.; For benzene each C–C link has 3 shared π‑bonds / 6 positions = 0.5; add the σ‑bond → total bond order 1.5.

[CHEM][BONDING][HIGH-YIELD] What are key points about Bond picture for ethyne (C2H2)?

Each carbon supplies two sp hybrids (colinear), giving; 1 C–C σ bond (sp–sp overlap); 2 C–H σ bonds (sp–s overlap); Remaining two p orbitals on each C overlap sideways twice → 2 π bonds.

[CHEM][BONDING][HIGH-YIELD] What are key points about Electron‑domain count → first stop in shape prediction?

2 domains → linear (180°); 3 domains → trigonal‑planar “umbrella” (120°)

[CHEM][BONDING][HIGH-YIELD] What are key points about Example: Drawing the Lewis Structure for CO2?

Each bond uses 2 electrons, so 4 electrons used, 12 remaining.; Place lone pairs on oxygen atoms to complete their octets.; O.. - C - ..O.. (dots represent lone pairs); 12 electrons placed on oxygens, 0 remaining.

[CHEM][BONDING][HIGH-YIELD] What are key points about How to calculate FC for any atom?

V = number of valence electrons in the free atom (Period‑table group).; B = total bonding electrons around the atom in the Lewis structure (count both electrons in every bond).; L = lone‑pair electrons on that atom.

[CHEM][BONDING][HIGH-YIELD] What are key points about Lattice energy (ΔHlatt)?

ionic charges are higher (MgO NaCl),; ionic radii are smaller (LiF CsF).

[CHEM][BONDING][HIGH-YIELD] What are key points about Relating Lewis structures, electron domains & hybridization?

Draw the Lewis structure ➜ count electron domains around the central atom.; Domains = 2 → sp; 3 → sp2; 4 → sp3.; Lone pairs occupy hybrid orbitals just like σ‑bond pairs; this can compress ideal angles (e.g. 107° in NH3, 104.5° in H2O).

[CHEM][BONDING][HIGH-YIELD] What are key points about Shortcut: predict shape ⇄ hybrid set?

tetrahedral domain arrangement ⇄ sp3; trigonal planar ⇄ sp2; linear ⇄ sp; trigonal bipyramidal ⇄ sp3d

[CHEM][BONDING][HIGH-YIELD] What are key points about Trends to remember?

Electron count ↑ → dispersion ↑ → boiling point ↑; Chain length ↑ / branching ↓ → surface area ↑ → dispersion ↑; Molecular polarity; Hydrogen bonding needs the “HFON” trio

[CHEM][BONDING][HIGH-YIELD] What are key points about Visualising and quoting dipoles?

δ+ … δ‑ notation labels the partial charges.; A vector arrow → drawn along the bond (arrow head toward δ‑) indicates both direction and relativemagnitude of the dipole.

[CHEM][BONDING][HIGH-YIELD] What are key points about VSEPR theory: shapes arise from electron‑domain repulsion?

The number of domains dictates the ideal electron‑domain geometry (EDG).; The placement (or absence) of bonding pairs within that EDG gives the observable molecular geometry(MG).

[CHEM][BONDING][HIGH-YIELD] What are key points about When both electrons in the bond come from the same atom?

Use an arrow → (or occasionally ⟶ ) to show the direction of donation.; Formation of a dative bond often converts an electron‑deficient species into a stable octet.

[CHEM][BONDING][HIGH-YIELD] What are key points about When polarity does survive?

the bonds are of different polarities (e.g. H‑Cl vs C‑H in CH3Cl), or; the geometry is asymmetric so that identical dipoles do not cancel (e.g. NH3, H2O).

[CHEM][BONDING][HIGH-YIELD] What are key points about When to expect it?

A double or triple bond can be placed in two or more positions without breaking the octet (or expanded‑octet) rules.; The atoms involved must have parallel p‑orbitals to allow a continuous overlap for the delocalised electrons.

[CHEM][BONDING][HIGH-YIELD] What controls the strength?

Number of electrons / molar mass — ↑ electrons → ↑ force — More electrons = more polarisable cloud, bigger instantaneous dipoles.; Molecular surface area — Greater contact → ↑ force — Long, unbranched chains pack together better than compact branched isomers.; Shape / planarity — Flat, rigid molecules stack efficiently → ↑ force — E.g. iodine crystals or graphite layers.

[CHEM][BONDING][HIGH-YIELD] What should you know about Comparing different bonds within one molecule?

C–O (single) — 143 — 358; C=O (double) — 122 — 804

[CHEM][BONDING][HIGH-YIELD] What should you know about Key features?

0 lone pairs — trigonal planar 120° (e.g. ethene C2H4); 1 lone pair — bent / V‑shaped ≈ 118° (e.g. SO2)

[CHEM][BONDING][HIGH-YIELD] When polarity does survive?

CH3Cl tetrahedral — C–Cl dipole does not cancel with the three weaker C–H dipoles → overall vector toward Cl.; NH3 trigonal‑pyramidal — Three N–H dipoles point toward the lone‑pair apex, add to give a net vector along the N → LP axis.; H2O bent ≈ 105° — Two identical O–H dipoles are not colinear (bent shape) → vector sum toward oxygen.

[CHEM][BONDING][HIGH-YIELD] When to expect it?

A double or triple bond can be placed in two or more positions without breaking the octet (or expanded‑octet) rules.; The atoms involved must have parallel p‑orbitals to allow a continuous overlap for the delocalised electrons.

[CHEM][BONDING][HIGH-YIELD] Which One is True?

Both Perspectives Are Valid Intramolecular Context: When discussing the formation of a compound and the bond within a single formula unit of that compound, ionic bonds are intramolecular.

[CHEM][BONDING][APPLICATION] How chemists draw resonance?

Draw every valid Lewis formula that keeps octets but places the π‑bond in a different position.; Connect the drawings with a double‑headed arrow ( ↔ ). Example for ozone: O=O–O ↔ O–O=O; The real molecule/ion is the resonance hybrid – one, lower‑energy structure that cannot be depicted by a single Lewis picture.

[CHEM][BONDING][APPLICATION] How do they arise?

Electron clouds are mobile. At any instant the electrons in an atom may be slightly closer to one side → an instantaneous dipole.; This temporary dipole induces a dipole in a neighbouring particle by repelling / attracting its electrons → an induced dipole.

[CHEM][BONDING][APPLICATION] How sigma bonds form?

s + s – H + H → H2; p + p (end‑on) – F + F → F2; s + p – H + F → HF (or hybrid + orbital overlaps in general); Any single covalent bond is a σ bond. In multiple bonds (double/triple) it is always the first bond to form; additional bonds are π bonds.

[CHEM][BONDING][APPLICATION] How to calculate FC for any atom?

V = number of valence electrons in the free atom (Period‑table group).; B = total bonding electrons around the atom in the Lewis structure (count both electrons in every bond).; L = lone‑pair electrons on that atom.

[CHEM][BONDING][APPLICATION] What is the sequence for 📌Easy Steps for Drawing Lewis Structures and Common Exceptions?

Determine the Total Number of Valence Electrons → Write the Skeleton Structure → Connect Atoms with Single Bonds → Distribute Remaining Electrons → Form Double or Triple Bonds if Necessary → Check for Formal Charges

[CHEM][BONDING][APPLICATION] Why carbon is special?

Forms strong C–C σ‑bonds.; Can use sp, sp2 or sp3 hybridisation → varied bond angles & dimensionality.; π‑electrons may delocalise, giving electrical conductivity in some forms.

[CHEM][BONDING][APPLICATION] Why learn Lewis structures?

predicting VSEPR shapes and bond angles; locating regions of charge for polarity & inter‑molecular forces; writing reaction mechanisms (lone‑pair and arrow‑pushing logic); estimating bond enthalpies, lengths, and relative bond strengths

[CHEM][BONDING][APPLICATION] Why length and strength correlate?

For a given pair of atoms, the potential‑energy curve has a single minimum where attractive forces (nucleus–electron, nucleus–shared pair) exactly balance repulsions. If the atoms are smaller or the shared electron density is greater the well deepens and its minimum shifts left – the bond becomes shorter and stronger.

[CHEM][BONDING][APPLICATION] Why resonance matters?

Extra stability – delocalisation lowers energy (benzene is surprisingly unreactive).; Uniform bond lengths – bonds become identical and intermediate (e.g. C–O bonds in CO32−).; Charge distribution – spreading charge influences acidity/basicity and solubility (carboxylate vs. carboxylic acid).; Spectroscopy – identical bonds give single IR peaks or NMR environments.

[CHEM][BONDING][APPLICATION] Why their properties differ?

Dimensionality – diamond & SiO2 are 3‑D networks → rigid, insulating; graphite/graphene are 2‑D sheets → lubricating & conductive.; Electron mobility – delocalised π‑systems in sp2 networks carry charge and heat.

[CHEM][BONDING][RECALL] What is the coordination number in a CsCl-type ionic lattice?

8

[CHEM][BONDING][RECALL] What are dipole-dipole interactions?

Intermolecular attractions between permanent partial charges in polar molecules.

[CHEM][BONDING][RECALL] What is the coordination number in a NaCl (rock-salt) lattice?

6 for each ion.

[CHEM][CHEMISTRY-FOUNDATIONS][HIGH-YIELD] What are high-yield facts to remember about Pressure and Other Different State Changes (12)?

Sublimation – iodine crystals, dry ice (CO2), and “smoke” from solid NH4Cl jump straight from solid to vapour at atmospheric pressure.; Deposition – snowflakes and window frost grow when water vapour locks directly into an ice lattice.; solid — liquid — melting / fusion — heat in; liquid — solid — freezing — heat out

[CHEM][CHEMISTRY-FOUNDATIONS][HIGH-YIELD] What are high-yield facts to remember about States of Matter (9)?

Spacing — Close‑packed — Touching but mobile — Far apart; Inter‑particle forces — Strong — Weaker — Negligible; Shape — Fixed — No fixed shape — No fixed shape; Volume — Fixed — Fixed — No fixed volume

[CHEM][CHEMISTRY-FOUNDATIONS][HIGH-YIELD] What are key points about How many elements are there??

The official list runs to 118, from hydrogen (1) to oganesson (118).; About 92–94 occur naturally; the rest are created in particle accelerators.

[CHEM][CHEMISTRY-FOUNDATIONS][HIGH-YIELD] What are key points about Kinetic theory link?

The hotter a sample is, the faster its particles move on average.; Average kinetic energy (KE) is proportional to absolute temperature T in kelvin.; For one particle, KE = ½ m v2 (m = mass, v = speed).

[CHEM][CHEMISTRY-FOUNDATIONS][HIGH-YIELD] What are key points about Reading a chemical formula?

Each element keeps its symbol (Na, Cl, O, …).; No subscript means “one”.