Q.1 Who proposed the modern periodic table based on atomic number?
Dmitri Mendeleev
Henry Moseley
John Dalton
Lothar Meyer
Explanation - Henry Moseley, in 1913, showed that the atomic number, not atomic mass, should be the basis of the periodic table.
Correct answer is: Henry Moseley
Q.2 Which of the following elements has the highest electronegativity?
Fluorine
Oxygen
Chlorine
Nitrogen
Explanation - Fluorine is the most electronegative element in the periodic table due to its small size and high effective nuclear charge.
Correct answer is: Fluorine
Q.3 The atomic radius of elements generally ______ across a period from left to right.
Increases
Decreases
Remains the same
First increases then decreases
Explanation - Atomic radius decreases across a period due to increasing nuclear charge, which pulls electrons closer to the nucleus.
Correct answer is: Decreases
Q.4 Which group of elements is also called the 'inert gases'?
Group 1
Group 17
Group 18
Group 2
Explanation - Group 18 elements are called inert or noble gases because they have complete valence electron shells and are chemically stable.
Correct answer is: Group 18
Q.5 Ionization energy generally ______ down a group in the periodic table.
Increases
Decreases
Remains constant
First decreases then increases
Explanation - Ionization energy decreases down a group because outer electrons are farther from the nucleus and experience less attraction.
Correct answer is: Decreases
Q.6 Which of the following is a halogen?
Fluorine
Sodium
Calcium
Helium
Explanation - Halogens belong to Group 17 and include Fluorine, Chlorine, Bromine, Iodine, and Astatine.
Correct answer is: Fluorine
Q.7 Which element is the most metallic in nature?
Cesium
Fluorine
Oxygen
Nitrogen
Explanation - Metallic character increases down a group and decreases across a period. Cesium, being low in the group, is highly metallic.
Correct answer is: Cesium
Q.8 Which element has the smallest atomic radius?
Lithium
Beryllium
Fluorine
Neon
Explanation - Atomic radius decreases across a period due to increasing nuclear charge; Neon, at the end of the period, has the smallest radius.
Correct answer is: Neon
Q.9 The elements in a group have the same number of ______.
Protons
Neutrons
Valence electrons
Energy levels
Explanation - Elements in the same group have the same number of valence electrons, which explains their similar chemical properties.
Correct answer is: Valence electrons
Q.10 Which property increases across a period due to increasing nuclear charge?
Atomic radius
Metallic character
Electronegativity
Reactivity of alkali metals
Explanation - Electronegativity increases across a period because atoms more strongly attract shared electrons as nuclear charge increases.
Correct answer is: Electronegativity
Q.11 Which of the following elements is an alkaline earth metal?
Sodium
Magnesium
Potassium
Chlorine
Explanation - Alkaline earth metals belong to Group 2, which includes Beryllium, Magnesium, Calcium, etc.
Correct answer is: Magnesium
Q.12 Which of these elements has the lowest first ionization energy?
Lithium
Potassium
Beryllium
Sodium
Explanation - Ionization energy decreases down a group; Potassium is the lowest among the given options.
Correct answer is: Potassium
Q.13 Which of the following is true about noble gases?
They are highly reactive
They have full valence shells
They are good conductors of electricity
They form ionic compounds easily
Explanation - Noble gases have complete valence shells making them chemically stable and largely unreactive.
Correct answer is: They have full valence shells
Q.14 Which element is more reactive: Chlorine or Fluorine?
Chlorine
Fluorine
Both are equally reactive
Depends on the compound
Explanation - Fluorine is the most reactive halogen due to its high electronegativity and small size.
Correct answer is: Fluorine
Q.15 In the modern periodic table, periods are arranged based on ______.
Increasing atomic mass
Increasing atomic number
Decreasing atomic radius
Increasing electronegativity
Explanation - Modern periodic table arranges elements in order of increasing atomic number as proposed by Moseley.
Correct answer is: Increasing atomic number
Q.16 Which property generally decreases across a period?
Electronegativity
Ionization energy
Atomic radius
Electron affinity
Explanation - Atomic radius decreases across a period because electrons are drawn closer to the nucleus due to higher nuclear charge.
Correct answer is: Atomic radius
Q.17 Which of the following elements is a transition metal?
Titanium
Calcium
Aluminum
Oxygen
Explanation - Transition metals are d-block elements, which include Titanium, Iron, Copper, etc.
Correct answer is: Titanium
Q.18 The property of elements to exhibit more than one oxidation state is called ______.
Electronegativity
Ionization energy
Variable valency
Atomic radius
Explanation - Many transition metals exhibit multiple oxidation states due to the involvement of d electrons.
Correct answer is: Variable valency
Q.19 Which element is most likely to form a cation with a +1 charge?
Sodium
Oxygen
Chlorine
Fluorine
Explanation - Alkali metals like Sodium have one valence electron, which they lose to form +1 cations.
Correct answer is: Sodium
Q.20 Which of the following has the highest electron affinity?
Chlorine
Sodium
Potassium
Calcium
Explanation - Chlorine has the highest tendency to gain an electron due to its high electronegativity and small size.
Correct answer is: Chlorine
Q.21 Which of the following is true about metals in the periodic table?
They are poor conductors
They are usually solid at room temperature
They have high ionization energy
They are highly electronegative
Explanation - Most metals are solid at room temperature (except mercury), good conductors, and tend to lose electrons.
Correct answer is: They are usually solid at room temperature
Q.22 Which group contains elements that are highly reactive non-metals?
Group 1
Group 2
Group 17
Group 18
Explanation - Group 17 elements are halogens, which are highly reactive non-metals.
Correct answer is: Group 17
Q.23 Which of the following elements has the highest metallic character?
Potassium
Calcium
Aluminum
Silicon
Explanation - Metallic character increases down a group and decreases across a period; Potassium is the most metallic among these.
Correct answer is: Potassium
Q.24 Which of the following is true about the periodic law?
Properties repeat after equal number of atoms
Properties repeat after equal number of neutrons
Properties repeat periodically when elements are arranged by atomic number
Properties do not show any regular pattern
Explanation - The modern periodic law states that chemical and physical properties of elements repeat periodically when arranged in order of increasing atomic number.
Correct answer is: Properties repeat periodically when elements are arranged by atomic number