Super-hard periodic table quiz

Q: What does the super-hard periodic table quiz test?

Twenty conceptual questions on exchange energy, relativistic effects, VSEPR edge cases, and the semi-empirical mass formula. Six near-twin choices each.

Q: Can I print the super-hard quiz?

Yes. Print or download a blank paper from this page. After you submit, a marked paper is available.

Q: Where are my answers stored?

Only in this browser, under a ptw.quiz.relativity key. Incomplete attempts wipe when you leave. Nothing is sent to a server.

Question 1

Why is chromium 3d⁵ 4s¹ rather than the Madelung 3d⁴ 4s²?

Accepted Answer

Exchange energy of six parallel spins, plus avoiding a 4s pair, beats the 3d⁴ 4s² arrangement

Answer

3d is always below 4s, so 4s never holds electrons in the first transition row

Answer

Pauli exclusion forbids two electrons in 4s on chromium specifically

Answer

Chromium has only five valence electrons, so 4s cannot be occupied

Answer

4s pairing energy is smaller than 3d pairing energy, so 4s empties completely

Answer

Relativistic 4s contraction forces one electron into 3d already in period 4

Question 2

Fe²⁺ is [Ar] 3d⁶, not [Ar] 3d⁴ 4s², because:

Accepted Answer

After 3d occupancy, 4s lies above 3d, so the ion loses 4s first

Answer

4s never held electrons in neutral iron

Answer

Ionic iron must keep 4s² to satisfy Madelung

Answer

3d electrons are less penetrating than 4s in the cation, so 4s fills after ionization

Answer

Fe²⁺ is d⁴ because two 3d electrons leave with the 4s pair

Answer

Ligand-field splitting empties 4s in every isolated gas-phase ion

Question 3

Helium is placed in group 18, not group 2, because:

Accepted Answer

A closed 1s² shell gives noble-gas chemistry, even though ns² looks like an alkaline earth

Answer

Helium has two protons, so it belongs under beryllium by Z

Answer

The 32-column table puts He in group 2 as official IUPAC policy

Answer

Helium’s first ionization energy is close to beryllium’s

Answer

Helium forms He²⁺ the way beryllium forms Be²⁺ in water

Answer

The 1s subshell is the start of the p-block, so He is a pnictogen

Question 4

The gas-phase water angle is ~104.5° rather than 109.5° because:

Accepted Answer

Two lone pairs occupy more space than bonding pairs and squeeze H–O–H

Answer

Oxygen is exactly sp² hybridized in water

Answer

Hydrogen bonding in the gas-phase monomer closes the angle

Answer

Each O–H is a double bond, so VSEPR counts six domains

Answer

The spectroscopic angle is 109.5°; 104.5° is only the liquid

Answer

Oxygen has no lone pairs in the VSEPR count; core electrons do the squeeze

Question 5

A lone pair in AX₄E (seesaw) is equatorial, not axial, because:

Accepted Answer

Equatorial has two 90° neighbors; axial has three, so the lone pair avoids axial

Answer

Axial has more space because 180° is larger than 120°, so lone pairs go axial

Answer

Lone pairs are smaller than bonding pairs, so they occupy the tight axial sites

Answer

Bent’s rule puts the most electronegative substituents equatorial, and a lone pair counts as F

Answer

The 3c–4e axial bonds require the lone pair to sit on the axis

Answer

SF₄ is tetrahedral, so axial versus equatorial never arises

Question 6

4s fills before 3d in K and Ca, yet occupied 3d drops below 4s, because:

Accepted Answer

4s has lower n+ℓ and better penetration as a diffuse ns orbital; occupied (n−1)d then contracts and falls below ns

Answer

3d is always lower; textbooks reverse the order for historical reasons only

Answer

4s has more radial nodes than 3d, so 4s is always the higher orbital

Answer

Pauli exclusion blocks 3d until 4s is full, after which 3d is forced down

Answer

Relativistic mass-velocity terms invert 3d/4s only in period 4

Answer

The Madelung rule is exact for atoms and ions; 3d never drops

Question 7

Which statement about ⁵⁶Fe and ⁶²Ni is correct?

Accepted Answer

⁶²Ni has the highest binding energy per nucleon; ⁵⁶Fe has the lowest mass per nucleon

Answer

⁵⁶Fe holds both the highest B/A and the lowest mass per nucleon

Answer

⁶²Ni holds both records

Answer

⁵⁸Fe is the peak of both curves

Answer

Within SEMF they are identical, so the names are interchangeable

Answer

⁵²Cr is the unique maximum; Fe and Ni sit on a flat plateau of equal height

Question 8

Hf is nearly the same size as Zr, not a full shell larger, because:

Accepted Answer

Lanthanide contraction: 4f shields poorly, so Z_eff on Hf 6s/5d nearly matches Zr 5s/4d

Answer

Hf has fewer electrons than Zr

Answer

Relativistic expansion of 4f makes Hf larger and the extra shell cancels the other way

Answer

Zr is 4d² 5s² and Hf is 4d² 5s², so they are the same atom

Answer

They are isotopes of one element

Answer

Actinide 5f contraction, not 4f, is what pins Hf to Zr

Question 9

F is more electronegative than Cl, yet Cl has the more negative electron affinity, because:

Accepted Answer

The extra electron on tiny F is crowded in 2p; Cl’s 3p has more room, while bonded-atom χ still peaks at F

Answer

Electronegativity and electron affinity are the same quantity on two scales

Answer

Fluorine has a lower first ionization energy than chlorine

Answer

Chlorine is smaller than fluorine

Answer

Fluorine already has a closed 2p⁶ subshell as a free atom

Answer

The electron affinity of fluorine has not been measured

Question 10

Palladium is [Kr] 4d¹⁰ rather than [Kr] 4d⁸ 5s² because:

Accepted Answer

A closed 4d¹⁰ shell is lower than keeping 5s occupancy for Pd

Answer

Palladium has only eight valence electrons

Answer

5s does not exist in period 5

Answer

Pd follows chromium’s d⁵ s¹ pattern

Answer

Relativity empties 4d instead of 5s

Answer

Madelung requires 5s² for every period-5 metal

Question 11

Mercury is liquid at 25 °C mainly because:

Accepted Answer

Relativistic 6s contraction and stabilization weaken Hg–Hg metallic bonding

Answer

Mercury molecules are held by hydrogen bonds

Answer

Mercury is a noble-gas configuration in the atom

Answer

London forces are weak because Hg has no electrons

Answer

5d is empty, so the packing fraction is poor

Answer

The melting point is high and the familiar liquid is supercooled

Question 12

The asymmetry term in the semi-empirical mass formula exists because:

Accepted Answer

Pauli: extra neutrons occupy higher neutron orbitals, so light nuclei prefer N ≈ Z

Answer

Neutrons Coulomb-repel each other inside the drop

Answer

It is the surface-tension term of the liquid drop

Answer

It counts proton–proton pairing only

Answer

Magic numbers are written as the asymmetry term

Answer

The term is zero except for odd–odd nuclei

Question 13

A C=O double bond counts as one VSEPR domain, not two, because:

Accepted Answer

Both electron pairs of the double bond occupy one region of space around carbon

Answer

VSEPR ignores multiple bonds by definition

Answer

Carbon has no lone pairs, so only hydrogens are domains

Answer

The π bond sits at 90° to the σ bond and adds a second domain

Answer

VSEPR applies only to single bonds

Answer

The oxygen lone pairs are the second domain of the double bond

Question 14

2p has a nodal plane and 2s does not (angularly) because:

Accepted Answer

ℓ = 1 requires one angular node; ℓ = 0 has none (2s still has a radial node)

Answer

2s and 2p have identical node counts

Answer

2p has two radial nodes and no angular node

Answer

2s has an angular node in the xy-plane

Answer

Nodes appear only for n ≥ 3

Answer

The nodal plane is the Pauli-forbidden region between opposite spins

Question 15

Gas-phase Fe³⁺ is d⁵ rather than a 4s-containing configuration because:

Accepted Answer

Both 4s electrons and one 3d electron leave; 4s is empty in the ion

Answer

Fe³⁺ is [Ar] 4s² 3d³

Answer

Fe³⁺ is [Ar] 3d³ 4s²

Answer

Iron(III) keeps 4s¹ 3d⁴

Answer

The ion is d⁶ because only the 4s pair leaves

Answer

Fe³⁺ is isoelectronic with Zn

Question 16

Gold is yellow and relatively unreactive mainly because:

Accepted Answer

Relativistic 6s contraction and 5d expansion shift the optical 5d → 6s transition into the visible

Answer

Gold has a closed 3d¹⁰ shell like zinc, so it cannot oxidize

Answer

Gold’s first ionization energy is the lowest in group 11

Answer

Au⁺ is 4s⁰, which forbids color

Answer

The gold atom is a noble-gas configuration

Answer

Non-relativistic calculations already predict the yellow color

Question 17

The second ionization energy of Na is huge compared with that of Mg because:

Accepted Answer

Na⁺ is a neon core; the second electron comes from a closed shell. Mg⁺ is still 3s¹

Answer

Sodium has more protons than magnesium

Answer

Mg⁺ is already a noble-gas core

Answer

Sodium has two valence electrons

Answer

The two second-ionization energies are essentially equal

Answer

Na’s second IE is smaller because sodium is an alkali metal

Question 18

In AX₄E₂ (XeF₄), the second lone pair sits trans to the first, giving square planar, because:

Accepted Answer

Lone-pair–lone-pair 90° contacts are minimized by 180° placement

Answer

Lone pairs occupy adjacent (cis) sites so they can share a face

Answer

Square planar is AX₄E₀, so XeF₄ has no lone pairs

Answer

The first lone pair is axial and the second equatorial in an octahedron

Answer

VSEPR predicts tetrahedral XeF₄

Answer

Trans placement maximizes the number of 90° lp–lp contacts

Question 19

Lanthanides have stubbornly similar chemistry mainly because:

Accepted Answer

4f orbitals are core-like, shield poorly, and overlap little, so +3 dominates

Answer

4f orbitals hybridize like carbon sp³ and set the geometry

Answer

Lanthanides never form +3 ions

Answer

5f is filling in that row, not 4f

Answer

Every lanthanide has the same radius as lanthanum

Answer

4f electrons are more diffuse than 6s

Question 20

H₂O is bent while gaseous BeH₂ is linear because:

Accepted Answer

Water has two bonds plus two lone pairs (SN 4); BeH₂ has two bonds and no lone pairs (SN 2)

Answer

Both are SN 4; beryllium is just larger so the angle opens to 180°

Answer

BeH₂ is bent at 104.5° in the gas phase

Answer

Water is SN 2

Answer

Hydrogen bonding forces BeH₂ linear

Answer

Beryllium has two lone pairs in BeH₂

Super-hard periodic table quiz

Common questions

What does the super-hard periodic table quiz test?

Can I print the super-hard quiz?

Where are my answers stored?

Super-hard periodic table quiz

Common questions

What does the super-hard periodic table quiz test?

Can I print the super-hard quiz?

Where are my answers stored?