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Three elements A, B and C have 3, 4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, give their valencies.

Answer: A belongs to Group 13 B belongs to Group 14 C belongs to Group 2 Because the outermost shell of 'A' has three electrons, it belongs to... View Article

Write the formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by Mendeleev.

Answer: Germanium (Ge) is known as Eka-silicon. It belongs to Mendeleev's periodic table's group 4 and hence has a valency of 4. GeCl4 is the... View Article

“Hydrogen occupies a unique position in Modern Periodic Table”. Justify the statement.

Answer: The electron configuration of hydrogen is 1s1. It can either take the helium configuration, which is a stable configuration, or it can... View Article

In Mendeleev’s Periodic Table the elements were arranged in the increasing order of their atomic masses. However, cobalt with an atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give a reason for the same.

Answer: Mendeleev’s periodic table is an arrangement of elements in an increasing atomic mass order in a tablet form, such that it reflects... View Article

Can the following groups of elements be classified as Dobereiner’s triad? (a) Na, Si, Cl (b) Be, Mg, Ca Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40 Explain by giving reason.

Answer: Dobereiner’s triads were groups of elements with similar properties that were identified by the German chemist Johann Wolfgang... View Article

Elements have been arranged in the following sequence on the basis of their increasing atomic masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K (a) Pick two sets of elements which have similar properties. (b) The given sequence represents which law of classification of elements?

Answer: Dobereiner’s triads were groups of elements with similar properties that were identified by the German chemist Johann Wolfgang... View Article

The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements.

Answer: Such an arrangement of elements is called Triads. Dobereiner’s triads were groups of elements with similar properties that were... View Article

Which of the following set of elements is written in order of their increasing metallic character? (a) Be Mg Ca (b) Na Li K (c) Mg Al Si (d) C O N

Answer: (a) Be, Mg, Ca The term metallic character refers to a set of chemical characteristics that are linked with metals. The majority of... View Article

On moving from left to right in a period in the periodic table, the size of the atom. (a) increases (b) decreases (c) does not change appreciably (d) first decreases and then increases

Answer: (b) decreases Atomic radius is half the distance between adjacent atoms of the same element in a molecule. In general, the atomic radius... View Article

Which one of the following does not increase while moving down the group of the periodic table? (a) Atomic radius (b) Metallic character (c) Valence (d) Number of shells in an element

Answer: (c) Valence In a period, the number of valence electrons increases from left to right, while the number of valence electrons in a group... View Article

Which one of the following depicts the correct representation of the atomic radius(r) of an atom?

Answer: Atomic radius is half the distance between adjacent atoms of the same element in a molecule. In general, the atomic radius decreases... View Article

The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong? (a) Metal (b) Metalloid (c) Non-metal (d) Left-hand side element

Answer: (b) Metalloid Element with atomic number 14 is Silicon and is a metalloid. It forms an acidic oxide, thus behaving as a non- metal and... View Article

Which of the following elements will form an acidic oxide? (a) An element with atomic number 7 (b) An element with atomic number 3 (c) An element with atomic number 12 (d) An element with atomic number 19

Answer: (a) An element with atomic number 7 Element with atomic number 7 has electron configuration 2,5 which means it can gain 3 electrons and... View Article

Three elements B, Si and Ge are (a) metals (b) non-metals (c) metalloids (d) metal, non-metal and metalloid respectively

Answer: (c) metalloids Metalloids are a small group of elements founds in the periodic table of elements along the zigzag line that distinguishes... View Article

Arrange the following elements in the order of their increasing nonmetallic character Li, O, C, Be, F (a) F < O < C < Be < Li (b) Li < Be < C < O< F (c) F < O < C < Be < Li (d) F < O < Be < C < Li

Answer: (b) Li < Be < C < O < F The non-metallic character is the tendency of an element to accept electrons and form negative ions... View Article

Arrange the following elements in the order of their decreasing metallic character Na, Si, Cl, Mg, Al (a) Cl > Si >Al > Mg >Na (b) Na >Mg >Al >Si > Cl (c) Na > Al > Mg > Cl > Si (d) Al > Na> Si > Ca> Mg

Answer: (b) Na >Mg >Al >Si > Cl The term ''metallic character'' refers to a set of chemical characteristics that are linked with... View Article

Which of the following are the characteristics of isotopes of an element? (i) Isotopes of an element have the same atomic masses (ii) Isotopes of an element have the same atomic number (iii) Isotopes of an element show the same physical properties (iv) Isotopes of an element show the same chemical properties (a) (i), (iii) and (iv) (b) (ii), (iii) and (iv) (c) (ii) and (iii) (d) (ii) and (iv)

Answer: (d) (ii) and (iv) Elements with the same atomic number but different atomic masses are known as isotopes. Isotopes same chemical... View Article

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27	28	29	30