D and F Block Elements NEET Questions

Explanation: This question asks about the total number of series in the d-block of the Periodic Table, which are commonly known as transition series. Transition series are rows in the Periodic Table where the d-orbital electrons are progressively filled. They show recurring patterns in chemical properties like variable oxidation states, colored compounds, and magnetic behavior. To determine the number, one must identify how many separate rows contain elements with partially filled d-orbitals. Starting from scandium (or the first d-block element) and moving across to zinc (or the end of each d-block row) gives one series, and repeating this for subsequent periods counts the total number of transition series. For instance, the first series begins with scandium, the second with yttrium, and the third with lanthanum (considering the main transition elements, not lanthanides). Each series reflects the filling of 3d, 4d, or 5d orbitals in sequence. An analogy is like stair steps where each step represents a new row of elements showing similar behaviors but in higher energy levels. Overall, counting these distinct series provides a clear picture of the organization of d-block elements and their repeating chemical trends.

Explanation: This question focuses on the term “noble Metals,” which describes Metals that resist corrosion and oxidation under normal conditions. Platinum and gold fall into this category due to their chemical inertness. Key properties include high resistance to Acids, non-reactivity with oxygen in the air, and stability in harsh environments. Understanding why they are called noble involves comparing them with more reactive Metals like iron or copper, which readily oxidize or form compounds. The reasoning involves observing that platinum and gold rarely participate in chemical reactions with common reagents, maintaining their lustrous appearance over time. This property also explains their widespread use in jewelry and electrical contacts. For an analogy, noble Metals are like diplomats who avoid conflicts, staying “neutral” in chemical reactions. In summary, their minimal reactivity defines them as noble, distinguishing them from most other Metals that react readily with environmental agents.

Explanation: This question asks to identify the statement that does not correctly describe transition elements. Transition elements are characterized by the filling of d-orbitals and exhibit properties between s- and p-block elements. Key points include their variable oxidation states, the involvement of d-electrons in Bonding, and characteristic magnetic properties due to unpaired electrons. To reason, examine each statement carefully: one should check the electron configuration patterns, whether scandium truly has the smallest atomic number among transition elements, and if lanthanum is a transition element or a lanthanide. The key is understanding the definitions of transition elements versus lanthanides. For example, while scandium starts the first d-block series, lanthanum belongs to the f-block series (lanthanides). Analogously, it’s like distinguishing between cousins in a family—one group shares common traits, while another looks similar but belongs to a different branch. In summary, understanding the electron configurations and placement in the Periodic Table helps identify the exception among the statements.

Explanation: This question examines how oxidation states vary across a transition series. Transition elements often exhibit multiple oxidation states due to the involvement of both (n-1)d and ns electrons in Bonding. Key background includes the trend that early elements in a series have lower oxidation states, middle elements often reach higher oxidation states, and later elements may show a decrease. Step-by-step reasoning involves looking at how d-orbitals are filled progressively across the series, which influences the maximum number of electrons available for Bonding. For instance, in the first transition series, titanium can show +4, manganese reaches +7, and zinc is mainly +2. An analogy is climbing a hill: oxidation states rise as you reach the peak and decline afterward. In summary, the oxidation state pattern across a series is not uniform but follows a rise-and-fall trend influenced by electron configuration.

Explanation: This question focuses on the origin of paramagnetism in transition Metals. Paramagnetism is the property of being attracted to an external magnetic field, which arises due to the presence of unpaired electrons. Transition elements have partially filled d-orbitals, providing unpaired electrons that generate magnetic moments. Step-by-step reasoning involves examining the electron configuration of each element to determine the number of unpaired electrons. Paired electrons cancel their magnetic effects, so only unpaired electrons contribute. For analogy, unpaired electrons are like tiny bar magnets freely spinning inside the Atom, causing attraction when an external field is applied. In summary, paramagnetism directly relates to the number of unpaired electrons in the d-orbitals of transition Metals, explaining their magnetic behavior.

Explanation: This question is about identifying an element that exhibits ferromagnetism, a phenomenon where magnetic moments of atoms align parallel to each other in regions called domains. Ferromagnetism occurs in certain transition Metals with unpaired electrons in d-orbitals and strong exchange interactions between them. Reasoning involves recalling that only a few Metals like iron, cobalt, and nickel show this behavior at room temperature, while most transition elements are either paramagnetic or diamagnetic. An analogy is a crowd of dancers moving in perfect sync, creating a large combined effect, compared to random motion in paramagnetism. In summary, ferromagnetism arises from aligned unpaired electrons in specific elements, giving strong permanent Magnetism.

Explanation: This question deals with the classification of oxides based on their chemical behavior. Oxides can be acidic, basic, amphoteric, or neutral. CrO₃ contains chromium in a high oxidation state, which typically reacts with water to form an Acid. Key background includes the correlation between oxidation state and oxide nature: higher oxidation states often yield acidic oxides, while lower ones tend to form basic oxides. Step-by-step reasoning involves analyzing the compound’s reaction with water and Bases: CrO₃ reacts with water to form chromic Acid, demonstrating its acidic character. An analogy is how citrus juice reacts with baking soda to produce fizz, showing acidity. In summary, CrO₃ is recognized as an acidic oxide due to the high oxidation state of chromium and its reactions with water and Bases.

Explanation: This question asks to determine the oxidation number of chromium in potassium dichromate. Key concepts include the rules for assigning oxidation states: the sum of oxidation states in a neutral compound or polyatomic ion must equal the total charge. Step-by-step reasoning involves noting the charges of potassium (+1) and oxygen (-2) and setting up an equation to find chromium’s oxidation state. For example, in K₂Cr₂O₇, the total contribution from potassium and oxygen is known, allowing calculation of chromium’s value. An analogy is balancing weights on a scale: the total must sum to zero. In summary, using oxidation rules and charge balance enables determination of the chromium oxidation state in the compound.

Explanation: This question examines the concept of maximum oxidation states in transition metals. Oxidation states correspond to the number of electrons an element can lose or share in bonds. Key background: the highest oxidation state typically equals the total number of valence electrons, including both ns and (n-1)d electrons. Step-by-step reasoning involves identifying the element with the maximum number of valence electrons that can participate in Bonding without destabilizing the element. For instance, some transition metals in the middle of the series achieve very high oxidation states due to available d and s electrons. An analogy is using all your resources in a game to reach the maximum score. In summary, the highest oxidation state reflects the element’s ability to utilize all valence electrons in Chemical Bonding.