Classification of Elements and Periodicity in Properties
Test 5

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which element exhibits the most negative electron gain enthalpy?

Electron gain enthalpy becomes more negative across a period and less negative down a group. Among O, S, F, and Cl, Cl (group 17, period 3) has the most negative value due to its high effective nuclear charge and smaller size than S.

Cl
O
S
F
1

Which element in group 1 has the highest reactivity with water?

Reactivity with water increases down group 1 due to decreasing ionization enthalpy. Cs (lowest ionization enthalpy) reacts most vigorously among Li, Na, K, and Cs.

Li
Na
Cs
K
3

Which element in group 13 shows the maximum deviation from typical metallic character?

Metallic character increases down group 13. B (period 2) is a metalloid with minimal metallic properties, unlike Al, Ga, or In, which are more metallic.

Al
Ga
In
B
4

Which group 2 element has the highest lattice energy in its chloride compound?

Lattice energy increases with smaller cation size and higher charge density. \(\ce{BeCl2}\) (Be²⁺, smallest) has the highest lattice energy among Be, Mg, Ca, and Sr chlorides.

Be
Mg
Ca
Sr
1

Which group 1 element has the highest ionic conductivity in its molten chloride form?

Ionic conductivity in molten salts increases with smaller cation size due to higher mobility. LiCl has the highest conductivity among Li, Na, K, and Cs chlorides.

Li
Na
K
Cs
1

Which element in group 15 forms a pentoxide with the highest thermal stability?

Thermal stability of group 15 pentoxides (\(\ce{X2O5}\)) decreases down the group due to weaker X-O bonds. \(\ce{N2O5}\) is the most stable thermally, decomposing at a higher temperature than \(\ce{P2O5}\), \(\ce{As2O5}\), or \(\ce{Sb2O5}\).

P
As
N
Sb
3

Which element in the second period has the highest electron affinity?

Electron affinity increases across period 2. F has the highest electron affinity in period 2 (Li, Be, N, F), though less than Cl (period 3) due to electron repulsion in its compact 2p orbitals.

A. Li
B. Be
C. F
D. N
3

Which group 1 element has the highest flame coloration intensity due to its ionization energy?

Flame color intensity increases with lower ionization energy, allowing easier electron excitation. Cs (lowest ionization energy) exhibits the highest intensity among Li, Na, K, and Cs.

Cs
Li
Na
K
1

Which element has the electronic configuration \(1s^2 2s^2 2p^6 3s^2 3p^5\)?

Total electrons = 17, corresponding to Cl (period 3, group 17). Others: S (16 electrons), Ar (18 electrons), P (15 electrons).

S
Cl
Ar
P
2

Which group 16 element forms a dioxide that exists as a linear gas at room temperature?

In group 16, \(\ce{O2}\) is a linear diatomic gas at room temperature, unlike \(\ce{SO2}\) (bent), \(\ce{SeO2}\) (polymeric solid), or \(\ce{TeO2}\) (solid).

O
S
Se
Te
1

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