Think of the periodic table as a city map — every element has a fixed address (its position), a unique identity number (atomic number), and a neighbourhood that tells you its behaviour (group and period).
An element is a pure substance that cannot be broken down further by any ordinary chemical method. Right now, 118 elements are officially recognised. Each one is defined by a single number: its atomic number (Z), which is simply the count of protons in one atom of that element. Change the proton count and you have a different element entirely.
The mass number (A) is the total count of protons plus neutrons in the nucleus. So if you see A = 238, Z = 92 for uranium, you know it has 92 protons and 238 − 92 = 146 neutrons.
Now, Mendeleev arranged all known elements in the 19th century by increasing atomic mass, noticing that properties repeated at regular intervals — this is the periodic law. The modern periodic table, however, arranges elements by increasing atomic number, not mass. This small but critical difference resolved several anomalies that Mendeleev's original table had (for example, Argon vs. Potassium).
Here is the plain-language structure of the table:
A quick analogy: periods are like floors in a building, groups are like rooms on each floor. All rooms numbered "1" on every floor behave similarly — they're all the most reactive metals (alkali metals). All rooms numbered "18" are the most unsociable — the noble gases, which almost never react with anything.
The table is split into metals (left side and centre — about 80% of all elements), nonmetals (upper right), and a thin diagonal strip of metalloids (semi-metals like Silicon, Germanium) in between.
Every element on the periodic table has a unique atomic number Z. No two elements share the same Z. This is why the modern periodic law states: "Properties of elements are a periodic function of their atomic numbers."
Mass Number (A) = Protons (Z) + Neutrons (N)
Isotopes are atoms of the same element with the same Z but different A — meaning different neutron counts. Carbon-12 and Carbon-14 are both carbon (Z = 6), but Carbon-14 has two extra neutrons. This matters for the Bihar Police exam because uranium-235 (²³⁵U) is the fissile isotope used in nuclear reactors, while uranium-238 (²³⁸U) is far more abundant but not directly fissile.
Group 1 — Alkali Metals: Li, Na, K, Rb, Cs, Fr. All have one valence electron. Extremely reactive with water. Sodium (Na) and Potassium (K) are the most exam-relevant here.
Group 2 — Alkaline Earth Metals: Be, Mg, Ca, Sr, Ba, Ra. Two valence electrons. Calcium is critical for bones; Radium is radioactive.
Group 17 — Halogens: F, Cl, Br, I, At. One electron short of a full outer shell — therefore the most reactive nonmetals. Fluorine (F) is the most electronegative element in the entire table and is a nonmetal. This is a direct exam fact (see PYQ below).
Group 18 — Noble Gases: He, Ne, Ar, Kr, Xe, Rn. Full outer shells — chemically inert. Helium is used in balloons (lighter than air, non-flammable). Argon is used in welding.
Transition Metals (Groups 3–12): This block contains most of the industrially important metals — Iron (Fe), Copper (Cu), Zinc (Zn), Cobalt (Co), Nickel (Ni), Chromium (Cr), Manganese (Mn). Their compounds are typically coloured, which is a high-frequency exam topic.
Transition metal salts are coloured because of their partially filled d-orbitals. Learn these:
| Metal | Typical Salt Colour | Example | |---|---|---| | Copper (Cu) | Blue | CuSO₄·5H₂O (blue vitriol) | | Iron (Fe²⁺) | Light green | FeSO₄·7H₂O (green vitriol) | | Iron (Fe³⁺) | Yellow/Brown | Fe₂(SO₄)₃ | | Zinc (Zn) | White | ZnSO₄ | | Chromium (Cr) | Green/Violet | Cr₂O₃, CrCl₃ | | Cobalt (Co) | Pink/Blue | CoCl₂ |
Copper salts are blue — this has been asked directly (see PYQ).
Metals: Good conductors of heat and electricity, malleable (can be hammered into sheets), ductile (can be drawn into wires), lustrous (shiny). Most are solid at room temperature except Mercury (Hg), which is a liquid metal.
Nonmetals: Poor conductors (except Graphite, a form of Carbon), brittle in solid form, dull appearance. Examples: H, C, N, O, F, P, S, Cl, Se, Br, I, At, noble gases.
Look at the four options in the PYQ on nonmetals: F (Fluorine), Co (Cobalt), Na (Sodium), Fe (Iron). Three are metals; only Fluorine sits in Group 17 on the right side of the table — a nonmetal. That is the logic, not memorisation.
All elements with Z > 92 (beyond Uranium in the actinide series) are transuranium elements and are man-made. But the first element to be artificially synthesised was actually Technetium (Z = 43), which sits in the middle of the table. There is a gap in nature at position 43 because all its isotopes are radioactive and decay relatively quickly — so none survived from the early solar system. It was synthesised in 1937 by bombarding Molybdenum with deuterons (heavy hydrogen nuclei). The name itself comes from the Greek word for "artificial."
Plutonium (Z = 94) and Neptunium (Z = 93) were also synthesised artificially, but they came later. Francium (Z = 87) exists in nature (albeit in vanishingly small amounts as a radioactive decay product). So if a question asks "first artificially produced element," the answer is Technetium — not Plutonium, not Neptunium.
Uranium (Z = 92) is the fuel of nuclear fission reactors. When a slow neutron strikes a ²³⁵U nucleus, it splits into smaller nuclei and releases enormous energy (plus more neutrons that sustain the chain reaction). India's nuclear plants — like Tarapur, Kaiga, Narora — run primarily on uranium. This is a direct fact Bihar Police has tested.
When given element symbols with no other context, check position: metals dominate the left and centre of the table; nonmetals are upper-right. H, C, N, O, F, P, S, Cl, Br, I are the core nonmetals. Write them once as a list. Now for any option set with mixed metals and nonmetals, eliminate metals (Na, Fe, Co, Cu, Zn — all left/centre of table) and circle the nonmetal. Standard method: recall each element's block individually (20s per element). This pattern: one glance at symbol position eliminates 3 wrong options in under 5 seconds.
Use the phrase: "Cu-Blue, Fe-Green (ferrous), Fe-Brown (ferric), Zn-White." In any question about salt colours, map the colour directly to the metal. Copper sulfate is universally known as "blue vitriol" — this label is tested more often than the formula. Standard method: trial-and-error through all four salts (30s). This one-sentence pattern: direct match in 4 seconds.
Atomic number 43 has a visible "gap" in the table — no stable isotope. If any question says "first artificially made element," your brain should fire: Gap = 43 = Technetium. Contrast: Plutonium and Neptunium are also artificial but came after Technetium. Francium occurs naturally (barely). This single anchor eliminates three wrong options immediately. Step count: 1 recall step vs. comparing histories of four elements (4 steps).
In Hindi, ऊर्जा (Urja) means energy. The symbol U for Uranium directly sounds like "Urja." So: U = Urja = nuclear energy. Any MCQ asking which element powers a nuclear reactor — the moment you see "nuclear" or "atomic energy," write U, then match to Uranium in the options. This word-association eliminates the need to reason through cobalt, copper, and aluminium. Time: 3 seconds vs. 15 seconds for elimination of all four options individually.
The entire Group 17 column — F, Cl, Br, I, At — consists of nonmetals. If any option in a "which is nonmetal" question is from this group, pick it immediately. Fluorine (F) sits at the very top of Group 17 and is the most electronegative element. No calculation needed: Group 17 membership = nonmetal, guaranteed. Reduces a 4-option elimination to a 1-step group identification.
When you see a periodic table question in the exam hall, run this decision tree in order:
Step 1 — What is the question type?
Step 2 — If you are unsure of the symbol, recall the full name first (given in Hindi in many Bihar Police papers), then match to the symbol. Fe = Iron (लोहा), Cu = Copper (तांबा), Na = Sodium (सोडियम), Co = Cobalt, F = Fluorine (फ्लोरीन).
Step 3 — Eliminate by position. Metals are on the left; nonmetals on the right. Transition metals (Fe, Cu, Co, Zn, Cr, Mn, Ni) are in the middle block — all metals, all coloured salts.
Step 4 — If two options look similar (e.g., Plutonium vs. Technetium), anchor on the specific fact: "first" = Technetium 1937; "transuranium" = Z > 92.
Never spend more than 30 seconds on a GK/science fact question. If the framework does not resolve it in 30 seconds, mark your best guess and move on.
Why this question: The "first artificially produced element" question tests a specific fact that many candidates confuse with Plutonium (which is more famous due to atomic bombs). The trap is deliberate.
Solving path: Three distractors — Plutonium, Neptunium, Francium. Plutonium and Neptunium are both artificial but synthesised after 1937. Francium exists naturally as a radioactive decay product (tiny amounts, but natural). Only Technetium (Z=43) was the first to be deliberately synthesised in a lab (1937, by bombarding Molybdenum-98 with deuterons). Answer: Technetium.
Why this question: Nuclear energy questions appear repeatedly across UP Police, Bihar Police, and similar state exams. The Hindi phrasing ("परमाणु ऊर्जा") should not distract — the core fact is straightforward.
Solving path: Options: Uranium, Cobalt, Copper, Aluminium. Cobalt is used in radiotherapy (Co-60), not power generation. Copper and Aluminium are industrial conductors, not nuclear fuels. Uranium undergoes nuclear fission — the chain reaction that powers nuclear reactors. Apply the "U = Urja" anchor. Answer: Uranium (यूरेनियम).
Why this question: The metals vs. nonmetals question is the most basic periodic table test. The Hindi paper uses element symbols directly, so you need symbol-to-classification mapping.
Solving path: Four options — F, Co, Na, Fe. Na = Sodium (alkali metal, Group 1). Fe = Iron (transition metal). Co = Cobalt (transition metal). F = Fluorine (Group 17, halogen, nonmetal). Only Fluorine sits on the nonmetal side of the periodic table. Answer: F (Fluorine).
Why this question: Coloured salts is a recurring sub-topic in Bihar Police chemistry. Blue colour is almost exclusively linked to copper salts — this is a clean one-recall question if you have the fact stored.
Solving path: Options: Fe, Cu, Zn, Cr. Iron salts: ferrous = green (FeSO₄·7H₂O), ferric = yellow-brown. Zinc salts: white. Chromium salts: green or violet. Copper salts: blue — the classic example being Copper Sulphate (CuSO₄·5H₂O), called "blue vitriol" or नीला थोथा in Hindi. This Hindi name is sometimes directly quoted in papers. Answer: Cu (Copper).
Confusing Technetium with Plutonium as "first artificial element." Plutonium is more famous (nuclear weapons), but Technetium came first, in 1937. Plutonium was synthesised in 1940. This is the number-one trap in this question category.
Treating Francium as purely artificial. Francium (Z = 87) is indeed radioactive and extremely rare, but it does occur naturally as a product of radioactive decay. It is not "artificially produced" in the sense that Technetium is.
Identifying Cobalt (Co) as a nonmetal because it sounds unfamiliar. Co is a transition metal (Group 9, Period 4). Its symbol is sometimes confused with Carbon (C) or Chlorine (Cl). In the options, if you see Co next to F, do not hesitate — F is the nonmetal.
Mixing up green vitriol and blue vitriol. Green vitriol = Iron Sulphate (FeSO₄·7H₂O). Blue vitriol = Copper Sulphate (CuSO₄·5H₂O). A question giving "नीले रंग" (blue colour) means Copper, not Iron. The colour adjective is the only signal you need.
Using Uranium-238 instead of Uranium-235 for fission. For the exam, simply knowing "Uranium = nuclear energy" is sufficient. But if a question distinguishes isotopes, U-235 is the fissile fuel; U-238 is fertile (it can be converted to Plutonium-239 in a breeder reactor but does not directly sustain fission on its own).
Forgetting that Mercury (Hg) is a metal despite being liquid at room temperature. Mercury is a transition metal (Group 12, Period 6). If an MCQ asks "which metal is liquid at room temperature," the answer is Mercury — not a nonmetal, not an exception to the metal category.