RRB JE Periodic Table Questions with Detailed Solutions

The correct answer is (a) Groups.
· In the modern periodic table, the vertical columns are known as groups.
· Each group contains elements with similar chemical properties due to having the same number of electrons in their outer shell.
Information Booster:
· Table: Refers to the entire periodic table, not specifically to columns.
· Periods: Refers to the horizontal rows in the periodic table.
· Columns: A general term, but in the periodic table, these are specifically called groups.

The correct answer is (b) Atomic mass.
· Mendeleev's Periodic Law states that "The properties of elements are a periodic function of their atomic masses."
· Mendeleev arranged elements in his periodic table in order of increasing atomic mass, grouping elements with similar properties together.
· His arrangement allowed him to predict the existence of elements that had not yet been discovered, based on gaps in his periodic table.
Information Booster:
· Atomic Mass: The mass of an atom, which includes both protons and neutrons in the nucleus. It was the basis for Mendeleev’s arrangement.
· Modern Periodic Law: This law, introduced by Moseley, is based on atomic number rather than atomic mass, as atomic number better reflects the chemical properties of elements.
· Predictive Power: Mendeleev's periodic table allowed him to predict elements like gallium and germanium before they were discovered, showcasing the periodic law's utility.
· Neutrons and Atomic Radius: These factors were not known or considered in Mendeleev's time and do not serve as the basis of his periodic law.

The correct answer is (d) Bridge elements.
· Elements of the second period are referred to as bridge elements because they show similarities with both the elements of the group they belong to and elements in neighboring groups.
· They "bridge" the properties of elements across different groups.
Other Options:
· Typical elements: These usually refer to representative elements, not specifically second-period elements.
· Earth metals: This term refers to alkaline earth metals (Group 2 elements), not all second-period elements.
· Transition elements: These are elements in the d-block, whereas second-period elements are found in the p-block (except for hydrogen and helium).

The correct answer is (c) 16, 2.
The element with the atomic number 8 is Oxygen (O). To determine its group and period number:
1. Period Number: The period number is determined by the number of electron shells. Oxygen has 2 shells (K and L), so it belongs to Period 2.
2. Group Number: Oxygen has 6 valence electrons in its outermost shell (L-shell). It belongs to Group 16 (the Chalcogens) in the periodic table because elements in Group 16 typically have 6 valence electrons.
Information Booster:
· Atomic Number 8 corresponds to the element Oxygen.
· Group 16 elements are also known as the Chalcogens and include elements like Sulfur (S), Selenium (Se), and Tellurium (Te).
· Period 2 elements have two electron shells (K and L).
· Oxygen is a non-metal and a vital component for respiration and combustion processes.

The correct answer is (c) Atomic radius.
· As you move from left to right across a period in the periodic table, the atomic radius decreases. This is because the number of protons in the nucleus increases, leading to a stronger attraction between the nucleus and the electrons. This pulls the electrons closer to the nucleus, reducing the atomic radius.
· The increasing positive charge in the nucleus (due to more protons) attracts the electrons more strongly, pulling them closer to the center and decreasing the size of the atom.
Information Booster:
· Electron affinity: Electron affinity generally increases across a period because the atoms become more eager to gain electrons to complete their valence shell.
· Electronegativity: Electronegativity also increases across a period due to the increasing effective nuclear charge, which attracts bonding electrons more strongly.
· Ionisation energy: Ionisation energy increases across a period because the electrons are held more tightly by the higher positive charge in the nucleus, making it harder to remove an electron.

The correct answer is (c) Lithium.
· In the alkali metal group, the atomic size increases as you move down the group in the periodic table. This is because each element down the group has an additional electron shell, making the atoms larger.
· Lithium (Li) is the first element in the alkali metal group and has the smallest atomic size compared to the other alkali metals listed.
· As we move down the group from lithium to sodium, potassium, and rubidium, the atomic radius increases due to the addition of electron shells.
· Alkali metals include elements in Group 1 of the periodic table.
· They are highly reactive, especially with water, due to their single valence electron.
Additional Information:
· Potassium: Larger than lithium, sodium, and rubidium; it has more electron shells.
· Sodium: The second smallest among these, larger than lithium but smaller than potassium and rubidium.
· Lithium: The smallest in size, with only two electron shells, making it the correct answer.
· Rubidium: This is the largest among the options provided, as it is much further down the group.

The Correct answer is (a) Mosley.

• While Dmitri Mendeleev created the first periodic table in 1869, arranging elements by atomic mass, it was Henry Moseley who gave the modern form of the periodic table in 1913. He demonstrated that atomic number, not atomic mass, was the fundamental property determining the arrangement of elements.

• Moseley's work with X-ray spectra of elements led to the Modern Periodic Law, which states that "the physical and chemical properties of the elements are periodic functions of their atomic numbers."

• This shift from atomic mass to atomic number corrected many of the inconsistencies in Mendeleev's table and is the basis of the periodic table used today. Thus, Moseley's contribution led to the modern version of the periodic table.

Information Booster:
· Mosley: Contributed to the modern periodic table by establishing that elements should be arranged by atomic number.
· Einstein: Famous for his work in physics, particularly the theory of relativity.
· Bohr: Known for his model of the atom and contributions to quantum theory, but not for the periodic table.

The correct answer is (c) Decreases.
· As we move down a group in the periodic table, electron affinity decreases. This is because, as we go down a group, the atomic size increases, and the added electron is farther from the nucleus. As a result, the attraction between the nucleus and the added electron becomes weaker, leading to a lower electron affinity.
Information Booster:
· Electron affinity is the energy change that occurs when an atom gains an electron. Elements at the top of a group have a higher tendency to attract electrons due to their smaller atomic size.
Additional Information:
· Electron affinity generally increases across a period (left to right) and decreases down a group (top to bottom) in the periodic table.

The correct answer is (d) Valency.
While moving down a group in the periodic table:
· Metallic Character: Increases because elements tend to lose electrons more easily as the atomic size increases.
· Atomic Radius: Increases due to the addition of new electron shells, which increases the distance between the nucleus and the outermost electrons.
· Number of Shells in an Element: Increases as each successive element down the group has an additional electron shell.
· Valency:Does not increase consistently. The valency of elements in a group typically remains the same because they have the same number of valence electrons, which determines their chemical reactivity and bonding properties.
Information Booster:
· Metallic Character: Refers to the tendency of an element to lose electrons and form positive ions. It increases down a group as the attraction between the nucleus and the outer electrons decreases.
· Atomic Radius: The distance from the nucleus to the outermost shell of an atom. As new shells are added, the atomic radius increases down the group.
· Number of Shells: The number of electron shells increases by one as you move from one element to the next down a group.