SSC CGL Science – Matter & Atomic Structure – Level 2 · Exam Level · Tier I Sprint

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SSC CGL Science – Matter & Atomic Structure – Level 2 · Exam Level · Tier I Sprint – 15 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  
The number of electrons in the nitride ion N³⁻ (Z = 7) is:

Correct Answer: A [10]

Explanation:

Answer: 10. e = Z − charge = 7 + 3 = 10.

2.  
Match the followingMatch the colloid with its type:
P. Fog Q. Butter R. Milk
1. Emulsion 2. Aerosol 3. Gel

Correct Answer: D [P-2, Q-3, R-1]

Explanation:

Fog = liquid in gas (aerosol); butter = liquid in solid (gel); milk = liquid in liquid (emulsion).

3.  
Odd one outwhich of these does NOT sublime?

Correct Answer: C [Sodium chloride]

Explanation:

Common salt melts and boils at high temperatures; the others sublime.

4.  
An element X has the electronic configuration 2, 8, 7. The ion it most readily forms is:

Correct Answer: B [X⁻]

Explanation:

Seven outer electrons → gains 1 to complete the octet → X⁻ (like Cl⁻).

5.  
Chronological orderChronological order (earliest first):
1. Bohr's model 2. Dalton's atomic theory 3. Thomson's plum-pudding model 4. Rutherford's nuclear model

Correct Answer: B [2, 3, 4, 1]

Explanation:

Dalton 1808 → Thomson 1904 → Rutherford 1911 → Bohr 1913.

6.  
Assertion–Reason
A: Most α-particles passed straight through the gold foil in Rutherford's experiment.
R: Most of the space inside an atom is empty.

Correct Answer: C [Both A and R are true and R explains A]

Explanation:

The empty space lets most α-particles pass undeflected.

7.  
Two-quantity comparison
Quantity I: neutrons in ⁴⁰₁₈Ar
Quantity II: neutrons in ⁴⁰₂₀Ca

Correct Answer: A [Quantity I > Quantity II]

Explanation:

Ar: 40 − 18 = 22; Ca: 40 − 20 = 20.

8.  
How many moles are present in 66 g of carbon dioxide (C = 12, O = 16)?

Correct Answer: D [1.5]

Explanation:

M(CO₂) = 44 g/mol → 66 ÷ 44 = 1.5 mol.

9.  
Fractional distillation (rather than simple distillation) is used to separate two miscible liquids when:

Correct Answer: D [their boiling points are close to each other]

Explanation:

Close boiling points need a fractionating column; far-apart ones need only simple distillation.

10.  
Which pair of atoms are isobars?

Correct Answer: C [¹⁴C and ¹⁴N]

Explanation:

Isobars share the mass number (A = 14) but differ in Z; ¹²C/¹³C and ¹H/²H are isotopes; ²³Na/²⁴Mg are isotones (12 neutrons each).

11.  
25 g of sugar is dissolved in 100 g of water. The concentration of the solution (mass by mass) is:

Correct Answer: A [20%]

Explanation:

Solution = 125 g → 25/125 × 100 = 20% (divide by the solution, not the solvent).

12.  
Fill in the blankThe “plum-pudding” model of the atom was proposed by ___.

Correct Answer: B [J. J. Thomson]

Explanation:

Thomson (1904): electrons embedded in a sphere of positive charge.

13.  
True/false countHow many of these statements are true?
I. Evaporation causes cooling.
II. Evaporation increases when humidity increases.
III. Gases diffuse faster than liquids.
IV. Solids are highly compressible.

Correct Answer: C [2]

Explanation:

I and III are true; higher humidity slows evaporation; solids are almost incompressible.

14.  
Spot My Mistake“Al³⁺ (Z = 13, A = 27) has 13 protons, 14 neutrons and 16 electrons.” The correct number of electrons is:

Correct Answer: A [10]

Explanation:

A 3+ ion has LOST three electrons: 13 − 3 = 10.

15.  
The symbol Pb for lead comes from the Latin word:

Correct Answer: D [plumbum]

Explanation:

Pb = plumbum (the word ‘plumber’ comes from it).

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