201. The \(f\)-block is called the inner-transition block because the differentiating electron enters an inner
ⓐ. \(ns\) subshell
ⓑ. \(np\) subshell
ⓒ. \((n-1)d\) subshell
ⓓ. \((n-2)f\) subshell
Correct Answer: \((n-2)f\) subshell
Explanation: In \(f\)-block elements, the differentiating electron enters an \(f\) subshell that lies two principal shells inside the outermost shell. This is expressed as \((n-2)f\), where \(n\) represents the outermost principal shell. The \(s\)-block uses \(ns\), the \(p\)-block uses \(np\), and the \(d\)-block uses \((n-1)d\). Because the electron enters an inner \(f\) subshell, these elements are called inner-transition elements. The word inner refers to the subshell being filled, not to the elements being outside the periodic table.
202. For a period \(6\) inner-transition element, the \(f\) subshell associated with the \((n-2)f\) rule is
ⓐ. \(4f\)
ⓑ. \(3f\)
ⓒ. \(5f\)
ⓓ. \(6f\)
Correct Answer: \(4f\)
Explanation: \( \textbf{Given period:} \) Period \(6\), so the highest principal shell is \(n=6\).
\( \textbf{Rule for \(f\)-block:} \) The differentiating electron enters \((n-2)f\).
\( \textbf{Substitution:} \)
\[
(n-2)f=(6-2)f
\]
\[
(6-2)f=4f
\]
\( \textbf{Interpretation:} \) Period \(6\) inner-transition elements are associated with filling of \(4f\) orbitals.
\( \textbf{Final answer:} \) The relevant subshell is \(4f\). The \(6s\) electrons may be present, but the inner-transition identity comes from \(4f\) filling.
203. A period \(7\) inner-transition series is mainly associated with filling of the
ⓐ. \(5f\) subshell
ⓑ. \(4f\) subshell
ⓒ. \(6p\) subshell
ⓓ. \(7d\) subshell
Correct Answer: \(5f\) subshell
Explanation: \( \textbf{Given period:} \) Period \(7\), so \(n=7\).
\( \textbf{\(f\)-block relation:} \) Relevant subshell \(=(n-2)f\).
\[
(n-2)f=(7-2)f=5f
\]
\( \textbf{Series link:} \) The period \(7\) inner-transition series is connected with actinoid-type \(5f\) filling.
\( \textbf{Option check:} \) \(4f\) belongs to the period \(6\) lanthanoid-type filling, not the period \(7\) series.
\( \textbf{Final answer:} \) Period \(7\) inner-transition elements are associated mainly with \(5f\) filling. The period number and the \(f\)-subshell number differ by \(2\) in this notation.
204. The two series usually shown separately below the main body of the periodic table are
ⓐ. alkali metals and halogens
ⓑ. lanthanoids and actinoids
ⓒ. noble gases and alkaline earth metals
ⓓ. metalloids and noble gases
Correct Answer: lanthanoids and actinoids
Explanation: The \(f\)-block contains the lanthanoid and actinoid series. These elements are usually displayed below the main table to keep the long-form periodic table compact. Their separate placement is a layout choice, not a sign that they are outside the periodic system. Lanthanoids are associated mainly with \(4f\) filling, while actinoids are associated mainly with \(5f\) filling. Alkali metals, halogens, and noble gases belong to the main body of the table.
205. The table gives descriptions of periodic-table regions.
| Row | Description | Assigned region |
|---|
| P | Differentiating electron enters \(ns\) | \(s\)-block |
| Q | Differentiating electron enters \(np\) | \(p\)-block |
| R | Differentiating electron enters \((n-1)d\) | \(d\)-block |
| S | Differentiating electron enters \((n-2)f\) | \(p\)-block |
The row that needs correction is
ⓐ. Row P
ⓑ. Row Q
ⓒ. Row R
ⓓ. Row S
Correct Answer: Row S
Explanation: Row P is correct because \(ns\) filling identifies the \(s\)-block. Row Q is correct because \(np\) filling identifies the \(p\)-block. Row R is correct because \((n-1)d\) filling identifies the \(d\)-block. Row S is wrong because \((n-2)f\) filling identifies the \(f\)-block, not the \(p\)-block. The block name follows the subshell letter receiving the differentiating electron.
206. Match the series or region in Column I with its usual description in Column II.
| Column I | Column II |
|---|
| P. Lanthanoids | 1. Period \(7\) inner-transition series mainly linked with \(5f\) |
| Q. Actinoids | 2. Period \(6\) inner-transition series mainly linked with \(4f\) |
| R. \(d\)-block | 3. Groups \(3\) to \(12\) |
| S. \(p\)-block | 4. Groups \(13\) to \(18\) |
ⓐ. P-1, Q-2, R-3, S-4
ⓑ. P-2, Q-3, R-1, S-4
ⓒ. P-2, Q-1, R-3, S-4
ⓓ. P-4, Q-1, R-3, S-2
Correct Answer: P-2, Q-1, R-3, S-4
Explanation: Lanthanoids are the period \(6\) inner-transition series mainly associated with \(4f\) filling. Actinoids are the period \(7\) inner-transition series mainly associated with \(5f\) filling. The \(d\)-block occupies groups \(3\) to \(12\), while the \(p\)-block occupies groups \(13\) to \(18\). This matching connects the visual table layout with electronic subshell filling. The separate \(f\)-block display should not be confused with loss of periodic-table membership.
207. Use the arrangement described below: a long-form table is drawn in compact form, with the main body containing \(s\)-, \(d\)-, and \(p\)-block regions, while two rows are placed below the main body. These lower rows represent elements whose differentiating electron enters an inner \(f\) subshell. The lower rows are best described as
ⓐ. halogen rows
ⓑ. noble-gas rows
ⓒ. inner-transition series
ⓓ. ordinary group \(1\) rows
Correct Answer: inner-transition series
Explanation: The lower rows described are the lanthanoid and actinoid series. They are called inner-transition series because their differentiating electron enters an inner \(f\) subshell. Their placement below the table keeps the periodic table compact and avoids an extremely wide main body. These rows are still part of the atomic-number sequence of the periodic table. Halogens and noble gases are \(p\)-block groups in the main body, not the lower \(f\)-block rows.
208. A claim says, “The \(f\)-block is written below the table because its elements do not follow atomic number order.” The best evaluation is that the claim is
ⓐ. sound because lower placement means no atomic number sequence
ⓑ. weak because the lower placement is mainly a compact display of inner-transition elements
ⓒ. sound because \(f\)-block elements have no electronic configurations
ⓓ. weak only because all \(f\)-block elements are halogens
Correct Answer: weak because the lower placement is mainly a compact display of inner-transition elements
Explanation: The \(f\)-block elements do follow the atomic-number sequence within the periodic table. They are displayed below the main body mainly to keep the table compact and readable. If inserted into the main body, the table would become much wider. Their electronic configurations involve filling of inner \(f\) subshells, which justifies their special block identity. The lower placement is a drawing convention, not a rejection of periodic order.
209. Assertion: Actinoids are generally treated with awareness that many of them are radioactive.
Reason: Actinoids belong to the period \(7\) inner-transition series associated mainly with \(5f\) filling.
ⓐ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓑ. Both Assertion and Reason are true, and Reason explains Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, but Reason does not explain Assertion
Explanation: The Assertion is true because actinoids include many radioactive elements, a basic awareness usually attached to this series. The Reason is also true because actinoids are period \(7\) inner-transition elements associated mainly with \(5f\) filling. However, the \(5f\)-filling description identifies their block and series position; it does not by itself explain radioactivity. Radioactivity is a nuclear property, while \(5f\) filling is an electronic-configuration classification. The two statements are both valid but belong to different levels of explanation.
210. A configuration note mentions \((n-2)f^{1-14}\) filling along with outer \(ns\) electrons. The safest classification is
ⓐ. \(s\)-block representative element
ⓑ. \(p\)-block representative element
ⓒ. \(d\)-block transition element
ⓓ. \(f\)-block inner-transition element
Correct Answer: \(f\)-block inner-transition element
Explanation: The notation \((n-2)f^{1-14}\) is characteristic of \(f\)-block filling. The superscript range \(1\) to \(14\) reflects the maximum capacity of an \(f\) subshell. Even though outer \(ns\) electrons may appear in the configuration, the inner \(f\) subshell receiving the differentiating electron determines the block. Such elements belong to the inner-transition region. The presence of \(ns\) electrons alone should not lead to an \(s\)-block assignment.
211. In the periodic table, metals are found mainly on the
ⓐ. left side and central region
ⓑ. upper right corner only
ⓒ. noble-gas group only
ⓓ. line separating no elements
Correct Answer: left side and central region
Explanation: Metals occupy the left side and much of the central region of the periodic table. This includes the \(s\)-block metals and many \(d\)-block elements. Non-metals are concentrated mainly toward the upper right region, apart from hydrogen's special position. The arrangement reflects gradual changes in properties across a period. Metallic character generally decreases from left to right and increases down a group.
212. Non-metals are mainly located in the periodic table toward the
ⓐ. lower left region
ⓑ. centre of the \(d\)-block only
ⓒ. lanthanoid row only
ⓓ. upper right region
Correct Answer: upper right region
Explanation: Non-metals are concentrated toward the upper right region of the periodic table. This region includes elements such as oxygen, nitrogen, fluorine, chlorine, and the noble gases. Their position is connected with stronger attraction for electrons and lower metallic character compared with left-side metals. Hydrogen is a special non-metal placed separately because of its unique electronic structure. The upper-right location helps explain why non-metallic character increases across a period.
213. Metalloids are commonly found along the zig-zag boundary between metals and non-metals. A suitable example set is
ⓐ. \(\mathrm{Na}\), \(\mathrm{K}\), and \(\mathrm{Rb}\)
ⓑ. \(\mathrm{F}\), \(\mathrm{Cl}\), and \(\mathrm{Br}\)
ⓒ. \(\mathrm{B}\), \(\mathrm{Si}\), and \(\mathrm{Ge}\)
ⓓ. \(\mathrm{He}\), \(\mathrm{Ne}\), and \(\mathrm{Ar}\)
Correct Answer: \(\mathrm{B}\), \(\mathrm{Si}\), and \(\mathrm{Ge}\)
Explanation: Metalloids lie near the zig-zag boundary separating metals and non-metals. Common examples include \(\mathrm{B}\), \(\mathrm{Si}\), \(\mathrm{Ge}\), \(\mathrm{As}\), \(\mathrm{Sb}\), and \(\mathrm{Te}\). They show intermediate properties rather than behaving as typical metals or typical non-metals in every respect. \(\mathrm{Na}\), \(\mathrm{K}\), and \(\mathrm{Rb}\) are alkali metals, while \(\mathrm{F}\), \(\mathrm{Cl}\), and \(\mathrm{Br}\) are halogens. Noble gases form a separate unreactive family, not the metalloid boundary.
214. The table shows element-type locations. Select the row with the best description.
| Row | Type | Usual location |
|---|
| P | Metals | Left side and central region |
| Q | Non-metals | Only in the \(f\)-block |
| R | Metalloids | Only in group \(1\) |
| S | Noble gases | Mostly among alkali metals |
ⓐ. Row P
ⓑ. Row Q
ⓒ. Row R
ⓓ. Row S
Correct Answer: Row P
Explanation: Row P correctly describes the broad location of metals in the periodic table. Metals are mainly on the left and in the central region. Non-metals are mainly toward the upper right, not only in the \(f\)-block. Metalloids lie along the zig-zag boundary, not in group \(1\). Noble gases are in group \(18\), not among alkali metals.
215. Moving from left to right across a typical period, the broad change in element character is usually
ⓐ. metallic character increases continuously
ⓑ. all elements become identical in chemical behaviour
ⓒ. metallic character decreases and non-metallic character increases
ⓓ. non-metallic character disappears completely
Correct Answer: metallic character decreases and non-metallic character increases
Explanation: Across a period, the effective attraction of the nucleus for valence electrons generally increases. As a result, the tendency to lose electrons decreases, so metallic character decreases. At the same time, the tendency to attract or gain electrons generally increases, so non-metallic character increases. This explains the broad movement from metals on the left to non-metals on the right. The change is gradual, and metalloids often appear near the boundary region.
216. A period contains a left-side metal, a middle boundary element, and an upper-right non-metal. The middle boundary element is most likely to show
ⓐ. purely alkali-metal behaviour in all compounds
ⓑ. noble-gas inertness with a full octet in every case
ⓒ. intermediate metalloid character
ⓓ. no relation to periodic trends
Correct Answer: intermediate metalloid character
Explanation: Elements near the boundary between metals and non-metals often show metalloid character. They may show some properties resembling metals and some resembling non-metals. This intermediate behaviour reflects their position in the gradual left-to-right change across the periodic table. They are not simply alkali metals or noble gases. The boundary region is important because it shows that element character changes gradually rather than by a sudden jump.
217. Use the arrangement described below: a diagonal zig-zag line separates a large metallic region on the left and centre from a non-metallic region toward the upper right. Elements close to this line include \(\mathrm{B}\), \(\mathrm{Si}\), \(\mathrm{Ge}\), \(\mathrm{As}\), \(\mathrm{Sb}\), and \(\mathrm{Te}\). These elements are best described as
ⓐ. alkali metals
ⓑ. metalloids
ⓒ. noble gases
ⓓ. actinoids only
Correct Answer: metalloids
Explanation: The described zig-zag line is the usual boundary between metals and non-metals in the periodic table. Elements lying close to this boundary commonly show intermediate properties and are called metalloids. \(\mathrm{B}\), \(\mathrm{Si}\), \(\mathrm{Ge}\), \(\mathrm{As}\), \(\mathrm{Sb}\), and \(\mathrm{Te}\) are standard examples. Alkali metals are far to the left in group \(1\), and noble gases are in group \(18\). Actinoids belong to the \(f\)-block, not to the ordinary metalloid boundary.
218. Consider the statements about metals, non-metals, and metalloids in the periodic table.
I. Metals occupy much of the left and central part of the table.
II. Non-metals are concentrated mainly toward the upper right.
III. Metalloids commonly lie along a zig-zag boundary.
IV. All elements in the \(p\)-block are metals.
The supported statements are
ⓐ. I and IV only
ⓑ. II and IV only
ⓒ. I, II, III, and IV
ⓓ. I, II, and III only
Correct Answer: I, II, and III only
Explanation: Statement I is true because metals dominate the left and central portions of the periodic table. Statement II is true because non-metals are mainly found toward the upper right. Statement III is also true because metalloids lie along the zig-zag boundary between metallic and non-metallic regions. Statement IV is false because the \(p\)-block includes metals, metalloids, non-metals, halogens, and noble gases. The \(p\)-block is a mixed-property region rather than an all-metal region.
219. A claim says, “Any element on the left side of a period should be more likely to lose electrons than an element on the upper right.” This claim is generally
ⓐ. unreasonable, because left-side elements are always noble gases
ⓑ. reasonable, because metallic character is stronger toward the left
ⓒ. reasonable only for \(f\)-block elements
ⓓ. unreasonable, because periodic position never relates to chemical behaviour
Correct Answer: reasonable, because metallic character is stronger toward the left
Explanation: Left-side elements of a period are generally more metallic and more electropositive. Metallic elements tend to lose electrons and form cations more readily than non-metals. Toward the upper right, elements generally show stronger non-metallic character and a greater tendency to attract electrons. This is a broad periodic trend, not a statement that every individual comparison ignores exceptions. The left-to-right change in character is one of the main uses of periodic classification.
220. The best summary of the metal-to-non-metal distribution in the periodic table is that
ⓐ. metals and non-metals are randomly scattered with no trend
ⓑ. metals, metalloids, and non-metals occupy regions that reflect a gradual change in properties across periods
ⓒ. every element along the zig-zag line is an alkali metal
ⓓ. all non-metals belong to the \(d\)-block
Correct Answer: metals, metalloids, and non-metals occupy regions that reflect a gradual change in properties across periods
Explanation: The periodic table shows a broad property map. Metals are mainly on the left and in the centre, non-metals are mainly toward the upper right, and metalloids lie along the boundary between them. This arrangement reflects gradual changes in electron-loss and electron-attraction tendencies across periods. It also helps predict whether an unfamiliar element is likely to behave as a metal, non-metal, or metalloid. The distribution is trend-based, not random.
