Question 1

The element with the highest electronegativity value in the periodic table is:

Accepted Answer

Fluorine (F) has the highest electronegativity (3.98 on Pauling scale) due to its small size and high nuclear charge.

Question 2

Which period of the periodic table contains the first lanthanide series element?

Accepted Answer

The lanthanides (4f-block) begin in Period 6 with Lanthanum (La, atomic number 57).

Question 3

Atomic radius generally increases down a group because:

Accepted Answer

Adding new electron shells as you move down a group increases atomic radius despite increasing nuclear charge.

Question 4

Which element belongs to Group 17 (Halogens) and Period 3?

Accepted Answer

Chlorine (Cl) is located at Group 17, Period 3 with electron configuration [Ne]3s²3p⁵.

Question 5

Which of the following elements is a transition metal with atomic number 26?

Accepted Answer

Iron has atomic number 26 and belongs to the d-block transition metals in Period 4.

Question 6

Ionization energy increases across a period and decreases down a group. Which of the following elements has the highest first ionization energy?

Accepted Answer

Neon (2s² 2p⁶) has the highest first ionization energy among these noble gases due to its small size and stable valence configuration.

Question 7

An element belongs to Group 17 and Period 3 of the periodic table. Identify this element and its electron configuration.

Accepted Answer

Group 17, Period 3 corresponds to Chlorine (Z = 17) with configuration [Ne] 3s² 3p⁵, having 7 valence electrons.

Question 8

The element with atomic number 35 belongs to which block and group of the periodic table?

Accepted Answer

Element with Z = 35 is Bromine (Br) with configuration [Ar] 3d¹⁰ 4s² 4p⁵, belonging to p-block and Group 17 (halogens).

Question 9

Which of the following statements correctly describes the periodic trend for atomic radius down a group?

Accepted Answer

Down a group, atomic radius increases because new electron shells are added, outweighing the effect of increased nuclear charge.

Question 10

Which pair of elements shows the expected trend in electronegativity according to periodic law?

Accepted Answer

Electronegativity decreases across a period from left to right is incorrect; F > Cl correctly shows the trend that fluorine is more electronegative than chlorine.

Question 11

Which of the following elements exhibits the highest electronegativity value on the Pauling scale?

Accepted Answer

Fluorine has the highest electronegativity (4.0) among all elements due to its small atomic size and high nuclear charge.

Question 12

The atomic radius generally decreases across a period in the periodic table. Which factor is primarily responsible for this trend?

Accepted Answer

Across a period, nuclear charge increases while electrons are added to the same shell, causing increased nuclear attraction and reduced atomic radius.

Question 13

Which element is a transition metal with atomic number 24 and exhibits multiple oxidation states?

Accepted Answer

Chromium (Z = 24) is a d-block transition metal known for variable oxidation states ranging from +2 to +6.

Question 14

The first ionization energy of nitrogen (7N) is higher than that of oxygen (8O), despite oxygen having a greater nuclear charge. Which of the following best explains this anomaly in periodicity?

Accepted Answer

The extra stability of nitrogen's half-filled 2p³ orbital makes it harder to remove an electron, overriding the expected trend based on nuclear charge alone.

Question 15

The electronegativity values for F, Cl, Br, and I are 3.98, 3.16, 2.96, and 2.66 respectively. This trend in Group 17 demonstrates the periodicity principle that electronegativity decreases down a group. Which of the following is the primary reason for this decrease?

Accepted Answer

As atomic size increases down the group due to additional electron shells, valence electrons are farther from the nucleus and experience weaker attraction, reducing electronegativity.

Question 16

Among the elements Li, Be, B, and C in Period 2, the atomic radius decreases in the order Li > Be > B > C. If the atomic radius of Li is 152 pm and that of C is 77 pm, which statement correctly reflects the periodicity of atomic radius within this period?

Accepted Answer

Within a period, nuclear charge increases while electrons are added to the same shell, so shielding remains relatively constant and effective nuclear charge increases, pulling electrons closer.

Agniveer (All) Classification of Elements & Periodicity

Classification of Elements & Periodicity — Practice Questions