periodic table

Who is historically considered the "father of chemistry" according to the material?

Antoine Lavoisier

State Dobereiner's Law of Triads regarding the atomic weight of elements.

The atomic weight of the middle element is the arithmetic mean of the weights of the other two elements in a triad.

Why was Dobereiner's Law of Triads ultimately rejected?

In some triads, all three elements possessed nearly identical atomic masses, violating the expected arithmetic mean relationship.

Define Newlands' Law of Octaves.

When elements are arranged by increasing atomic weight, every eighth element possesses properties similar to the first.

In a Lothar Meyer curve, which group of elements typically occupies the peaks?

The most strongly electropositive alkali metals.

According to Lothar Meyer's curve of atomic volume versus atomic mass, which elements are found on the descending positions?

Alkaline earth metals.

Which elements occupy the ascending positions on the Lothar Meyer curve?

The halogens.

What occupies the bottom-most positions on the Lothar Meyer curve?

Metalloids and transition metals.

In Mendeleev's original periodic table, what was the total number of vertical columns (groups)?

Eight vertical columns, numbered I to VIII.

Which specific group was added to Mendeleev's periodic table following the discovery of inert gases?

The zero group.

For elements with atomic numbers 104 to 118, how is the group number determined?

The last two digits of the atomic number provide the group number in the periodic table.

Provide the formula for the total number of elements in a period when the principal quantum number n is an odd number (1, 3, 5, …).

Total elements = 2 × ((n + 1) / 2)^2

Provide the formula for the total number of elements in a period when the principal quantum number n is an even number (2, 4, 6, …).

Total elements = 2 × ((n + 2) / 2)^2

Define the term "periodicity" in the context of chemistry.

The regular repetition of chemical and physical properties of elements at fixed intervals.

What is Effective Nuclear Charge (Zeff)?

The net positive charge attracting an electron in an atom, accounting for the shielding effect of other electrons.

Provide the mathematical relationship between effective nuclear charge (Zeff), atomic number (Z), and the shielding constant (σ).

Zeff = Z − σ

Rank the subshells (s, p, d, f) in order of decreasing shielding/screening effect effectiveness.

s > p > d > f

According to Slater's Rules, what is the value of the shielding constant (σ) for an electron in the (n−1) shell when calculating for an ns or np electron?

0.85

According to Slater's Rules, what is the value of the shielding constant (σ) for electrons in the (n−2) or lower shells when calculating for an ns or np electron?

1.0

What is the specific shielding constant (σ) value for 2-electron species such as He, Li+, or Be2+ according to Slater's Rules?

0.3

What is the Slater's Rule shielding constant (σ) for an electron in the nth shell (excluding the electron being calculated)?

0.35

How do Slater's Rules value the shielding constant (σ) for all electrons residing in shells inner to an nd or nf electron?

1.0

How does Zeff generally change for alkali metals from Na to Rb when calculated using Slater's Rules?

The Zeff value remains approximately constant at 2.20.

Define covalent radius.

Half of the internuclear distance between two atoms of the same non-metallic element bound by a single bond.

Define metallic radius (crystal radius).

Half of the internuclear distance between two adjacent metal ions in a metallic lattice.

Why is the covalent radius of an element always lower than its metallic radius?

Covalent bonding involves orbital overlap, bringing nuclei closer together, whereas metallic radius involves adjacent, non-overlapping ions.

Provide the Stevenson and Schoemaker formula for calculating the bond length of a heteronuclear single bond using electronegativities.

Bond length = rA + rB − 0.09 × |ΔEN|

What occurs to the atomic radius of Ga compared to Al due to transition contraction?

The atomic radius of Ga becomes smaller than Al because the poor shielding of the 3d electrons leads to a higher Zeff.

Explain the cause of lanthanoid contraction.

The poor shielding effect of 4f electrons results in a significant increase in Zeff, pulling the outer electrons closer and decreasing atomic size.

Define Ionisation Potential (IP) or Ionisation Enthalpy.

The minimum energy required to remove the most loosely bound electron from an isolated gaseous atom.

Why is ionisation enthalpy always calculated for an atom in its gaseous state?

To ensure the atom is isolated and free from interatomic forces present in solid or liquid states.

Rank the subshells (s, p, d, f) in order of decreasing penetration effect.

s > p > d > f

According to the stability rules for oxidation states, what is indicated if the difference between two successive ionisation potential values is less than 11 eV?

The higher oxidation state is more stable.

According to the stability rules for oxidation states, what is indicated if the difference between two successive ionisation potential values is greater than 16 eV?

The lower oxidation state is more stable.

Define Electron Gain Enthalpy (ΔegH).

The energy change occurring when a neutral isolated gaseous atom accepts an extra electron to form a gaseous anion.

Why is the first electron gain enthalpy for most elements negative, while the second is always positive?

Energy is released when the first electron is added, but energy is required to overcome electrostatic repulsion when adding a second electron to an anion.

Why does chlorine have a more negative electron gain enthalpy than fluorine?

Fluorine's 2p shell is very small, leading to high interelectronic repulsion that makes adding an extra electron more difficult than in chlorine.

Define electronegativity.

The tendency of an atom in a molecule to attract shared pairs of electrons towards itself.

Provide the formula for electronegativity on the Mulliken scale in eV/atom.

EN = (IP + EA) / 2

Provide the mathematical relationship for converting electronegativity from the Mulliken scale to the Pauling scale.

Pauling EN = Mulliken EN / 2.8

Provide the Henry-Smith (Hannay-Smith) equation for calculating percentage ionic character.

% Ionic character = 16 × ΔEN + 3.5 × (ΔEN)^2

State the Allred-Rochow formula for electronegativity.

EN = (0.359 × Zeff / r²) + 0.744

What is the inert pair effect as applied to Group 14 elements like Pb?

The reluctance of s-orbital electrons to participate in bonding due to poor shielding by d or f orbitals, making the +2 oxidation state more stable than +4.

Why are Pb4+ compounds considered very good oxidising agents?

Because Pb2+ is more stable than Pb4+ due to the inert pair effect, Pb4+ readily accepts electrons to reduce to Pb2+.

Define a diagonal relationship in the periodic table.

A similarity in properties between elements of the second period and elements diagonally below them in the third period.

List three examples of diagonal relationships between second- and third-period elements.

Li with Mg, Be with Al, and B with Si.

What three factors primarily cause the diagonal relationship between elements?

Small atomic size, similar charge/radius ratio, and high electronegativity.

Define a Lewis acid.

An electron pair acceptor, often possessing vacant orbitals.

Define a Lewis base.

An electron pair donor, typically an anionic species or one containing lone pairs.

How does the percentage of s-character in hybridisation affect electronegativity?

Electronegativity increases as the percentage of s-character increases (sp > sp² > sp³).

Which element has the highest electronegativity?

Fluorine (F), with a Pauling value of 4.0.

Which element has the lowest electronegativity (highest electropositivity)?

Caesium (Cs), approximately 0.7–0.79.

Why do noble gases have positive electron gain enthalpy?

They have stable, completely filled valence shells, so adding an electron requires energy.

In the transition series, why do atomic radii of Pd and Pt remain nearly the same?

Due to lanthanoid contraction in the sixth period, which offsets the expected increase in size.

State the general trend for Zeff when moving from left to right across a period for s- and p-block elements.

Zeff increases by 0.65 per element because Z increases by 1 while σ increases by only 0.35.

What is transition contraction (d-block contraction)?

The decrease in atomic radius caused by the poor shielding effect of d-electrons, leading to a higher effective nuclear charge on outer electrons.

How is the Van der Waals radius defined for noble gases?

Half of the distance between the nuclei of two adjacent, non-bonded atoms in the solid state.

Which radius is typically the largest for a non-metallic element: covalent, metallic, or Van der Waals?

Van der Waals radius.

What is the relationship between bond polarity and electronegativity difference (ΔEN)?

Bond polarity is directly proportional to the electronegativity difference.

In the 3d transition series, identify the element with the largest atomic radius.

Scandium (Sc).

For isoelectronic species, how does ionic radius vary with nuclear charge?

Ionic radius increases as nuclear charge decreases.

What is the shielding constant (σ) for a 1s electron in a 2-electron species like He?

0.30

According to the provided charts, what is the trend of metallic character down a group?

Metallic character increases as ionisation enthalpy decreases.

How does electronegativity difference (ΔEN) affect bond energy?

As electronegativity difference increases, bond energy also increases.

Why does the stability of the +1 oxidation state increase in the order Ga+ < In+ < Tl+?

Due to the increasing inert pair effect down the group, making the lower oxidation state more stable.

For a homoatomic molecule, what is the relationship between bond length and covalent radius?

Bond length = 2 × Covalent radius

What is the kernel of an atom?

The nucleus together with the inner (core) electrons remaining after removal of the valence electrons.

Between nitrogen and oxygen, which has the higher first ionisation enthalpy, and why?

Nitrogen, because of its stable half-filled 2p³ electronic configuration.

Compare the ionisation potentials of Be and B.

Be has a higher ionisation potential than B because of its stable filled 2s² configuration and greater penetration of the s orbital.

How many elements are found in the sixth period of the periodic table?

32

Which subshells are filled during the fourth period?

4s, 3d, and 4p

The range of atomic numbers for the actinoid series is ____ to ____.

90 to 103

According to Slater's Rules, for an ns/np electron, the shielding value for the nth shell is _____.

0.35

If the difference between two successive ionisation potential values is greater than 16 eV, the _____ oxidation state is stable.

Lower

By how much does the Effective Nuclear Charge (Zeff) increase when moving left to right across a period in d-block elements?

0.15

State the mathematical formula for calculating Effective Nuclear Charge (Zeff).

Zeff = Z − σ (where Z is the atomic number and σ is the screening constant)

According to Slater's Rules, what is the value of the screening constant (σ) for a remaining electron in the same ns/np shell (nth shell)?

0.35

In Slater's Rules for ns/np electrons, what is the shielding value for each electron in the (n−1) shell?

0.85

In Slater's Rules for ns/np electrons, what is the shielding value for each electron in the (n−2) or lower shells?

1.00

For 2-electron species (e.g., He, Li+, Be2+), what is the fixed value of the screening constant (σ) according to Slater's Rules?

0.30

According to Slater's Rules, what is the shielding value (σ) for electrons in the same nd or nf shell?

0.35

According to Slater's Rules for calculating nd/nf electron shielding, what is the fixed shielding value (σ) for all electrons in shells lower than the nth shell?

1.00

The formula to calculate the total number of elements in a period when the principal quantum number (n) is an odd number is _____.

2 × ((n + 1) / 2)^2

The formula to calculate the total number of elements in a period when the principal quantum number (n) is an even number is _____.

2 × ((n + 2) / 2)^2

Provide the formula for the total number of subshells in a period if n is an odd number.

(n + 1) / 2

Provide the formula for the total number of subshells in a period if n is an even number.

(n + 2) / 2

What is the simple formula for the covalent radius of a homoatomic molecule?

Covalent radius = Bond length / 2

State the Stevenson and Schoemaker formula for the bond length of a heteroatomic molecule (in Å).

Bond length = rA + rB − 0.09 × |ΔEN|

In the Stevenson and Schoemaker formula, what is the constant value used if the bond length is measured in picometres (pm) instead of Angstroms?

9 (Formula: Bond length = rA + rB − 9 × |ΔEN|)

On the Mulliken scale, what is the formula for electronegativity when IP and EA are given in eV/atom?

χ = (IP + EA) / 2

What is the numerical relationship used to convert electronegativity from the Mulliken scale to the Pauling scale?

Pauling EN = Mulliken EN / 2.8

State the formula for electronegativity on the Pauling scale using IP and EA in eV/atom.

χ = (IP + EA) / 5.6

State the formula for electronegativity on the Pauling scale using IP and EA in kJ/mol.

χ = (IP + EA) / 540

State the formula for electronegativity on the Pauling scale using IP and EA in kcal/mol.

χ = (IP + EA) / 129

According to the Henry-Smith equation, how is the % ionic character of a bond calculated from electronegativity difference (ΔEN)?

% Ionic character = 16 × ΔEN + 3.5 × (ΔEN)^2

What is the Allred-Rochow formula for electronegativity?

χ = (0.359 × Zeff / r²) + 0.744 (r in Å)

State the stability rule for oxidation states: if the difference between two successive ionization energies (ΔIE) is ≤ 11 eV, which oxidation state is stable?

The higher oxidation state

State the stability rule for oxidation states: if the difference between two successive ionization energies (ΔIE) is ≥ 16 eV, which oxidation state is stable?

The lower oxidation state

What is the formula for Ionic Potential (φ)?

Ionic Potential = Charge / Radius

How is the group number determined for elements with atomic numbers 104 to 118?

The last two digits of the atomic number give the group number