If atomic number of an element is 11, the correct name, symbol and valency are :
- A.Lithium, Li, 1
- B.Magnesium, Mg, 2
- C.Boron, B, 3
- D.Sodium, Na, 1
Correct answer
Explanation
The correct answer is D, Sodium, Na, 1. The element with atomic number 11 is sodium, and with one electron in its outermost shell its valency is 1. Sodium's 11 electrons are arranged as 2, 8, 1. It readily gives up the single outer electron to form the Na⁺ ion with a stable neon-like structure, which makes it a very reactive alkali metal of Group 1 that is stored under kerosene. Its symbol Na comes from its Latin name natrium. Common salt, sodium chloride (NaCl), is its best-known compound. Option A is wrong because lithium has atomic number 3 (configuration 2, 1); its valency is 1, but the atomic number does not match. Option B is wrong because magnesium has atomic number 12 (2, 8, 2) and valency 2. Option C is wrong because boron has atomic number 5 (2, 3) and valency 3. Exam tip: atomic numbers 11 to 13 = sodium (Na, 1), magnesium (Mg, 2), aluminium (Al, 3); Na from natrium, K from kalium.
Practice Questions
View allIn the joining of railway tracks, iron oxide is made to react with
- A.Aluminium
- B.Zinc
- C.Copper
- D.Tin
Show answer
Railway tracks are joined by the thermite process, in which aluminium powder reduces iron oxide to molten iron. The reaction is Fe₂O₃ + 2Al → 2Fe + Al₂O₃.
Read the full explanation →A car of mass 800 kg is travelling at a speed of 40 km/h on a straight road. A force of 1000 N is applied on it in the direction of its velocity for 12 s. Which one among the following is the final speed of the car?
- A.55 km/h
- B.60 km/h
- C.94 km/h
- D.104 km/h
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The force gives the car an extra 15 m/s, which is 54 km/h, and 40 + 54 = 94 km/h. By Newton's second law, acceleration a = F/m = 1000 N ÷ 800 kg = 1.25 m/s².
Read the full explanation →Consider the electromagnetic radiations having wavelengths 200 nm, 500 nm and 1000 nm. Which wavelength(s) of the following can make visual sensation to a human eye?
- A.200 nm and 500 nm
- B.500 nm and 1000 nm
- C.500 nm only
- D.200 nm and 1000 nm
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The human eye responds only to visible light, which lies roughly between 400 nm (violet) and 700 nm (red), and 500 nm is the only one of the three values in that range.
Read the full explanation →Bright light is found to emit from photographer's flashgun. This brightness is due to the presence of which one of the following noble gases?
- A.Argon
- B.Xenon
- C.Neon
- D.Helium
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A photographer's flash tube is filled with xenon, which gives an intense burst of white light when a high-voltage spark passes through it.
Read the full explanation →Storage of biological tissues such as blood, organs, semen requires low temperature which is achieved upon the usage of
- A.Liquid nitrogen
- B.Solid carbon dioxide
- C.Liquid air
- D.Helium
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Liquid nitrogen boils at about −196 °C, cold enough to stop almost all biological activity, and it is cheap, inert and safe to handle.
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