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Why did Rutherford select a gold foil in his α–ray scattering experiment?

Answer: Rutherford intended a metal sheet that could be as thin as appropriate for the scattering experiment. The most malleable of all known... View Article

Will ³⁵Cl and ³⁷Cl have different valencies? Justify your answer.

Answer: The combining capacity of an atom is known as its valency. The number of bonds that an atom can form as part of a compound is expressed... View Article

Write any two observations which support the fact that atoms are divisible

Answer: An atom is defined as the smallest individual particle of matter. Atom was the indivisible particle up till Dalton’s theory. Then... View Article

Is it possible for the atom of an element to have one electron, one proton and no neutron. If so, name the element.

Answer: Yes, Hydrogen is the element which is having only 1 proton and 1 electron and no neutron hence there is no repulsive force in the nucleus... View Article

Atomic models have been improved over the years. Arrange the following atomic models in the order of their chronological order (i) Rutherford’s atomic model (ii) Thomson’s atomic model (iii) Bohr’s atomic model (a) (i), (ii) and (iii) (b) (ii), (iii) and (i) (c) (ii), (i) and (iii) (d) (iii), (ii) and (i)

Answer: (c) (ii), (i) and (iii) Thomson atomic model was proposed by William Thomson in the year 1900. This model explained the description of... View Article

Which of the following statement is always correct? (a) An atom has equal number of electrons and protons. (b) An atom has equal number of electrons and neutrons. (c) An atom has equal number of protons and neutrons. (d) An atom has equal number of electrons, protons and neutrons.

Answer: (a) An atom has equal number of electrons and protons. An atom is electrically neutral because the number of protons is always equal to a... View Article

Which of the following in Fig. do not represent Bohr’s model of an atom correctly? (a) (i) and (ii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (i) and (iv)

Answer: (c) (ii) and (iv) The first shell can have a maximum of 2 electron and the second shell can have a maximum of 8 electrons hence... View Article

The electron distribution in an aluminium atom is (a) 2, 8, 3 (b) 2, 8, 2 (c) 8, 2, 3 (d) 2, 3, 8

Answer: (a) 2, 8, 3 Atomic number of aluminium = 13. Number of electrons is 13. The first two electrons will go in the 1s orbital. Since 1s can... View Article

An atom with 3 protons and 4 neutrons will have a valency of (a) 3 (b) 7 (c) 1 (d) 4

Answer: (c) 1 The combining capacity of an atom is known as its valency. The number of bonds that an atom can form as part of a compound is... View Article

The first model of an atom was given by (a) N. Bohr (b) E. Goldstein (c) Rutherford (d) J.J. Thomson

Answer: (d) J.J. Thomson Thomson atomic model was proposed by William Thomson in the year 1900. This model explained the description of an... View Article

Elements with valency 1 are (a) always metals (b) always metalloids (c) either metals or non-metals (d) always non-metals

Answer: (c) either metals or non-metals The valency of an element is the number of hydrogen atoms that can combine with or replace (either... View Article

In a sample of ethyl ethanoate (CH₃COOC₂H₅) the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it? (a) One of the oxygen atoms has gained electrons (b) One of the oxygen atoms has gained two neutrons (c) The two oxygen atoms are isotopes (d) The two oxygen atoms are isobars.

Answer: (c) The two oxygen atoms are isotopes Isotopes is defined as variants of a particular element where these variants will have the same... View Article

Identify the Mg2+ ion from the Fig. where, n and p represent the number of neutrons and protons respectively.

Answer: (d) Number of protons in Mg atom = 2 + 8 + 2 = 12 Number of neutrons in Mg atom = 24 - 12 = 12 As mass number of Mg atom = 24 and number... View Article

The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion? (a) 13 (b) 10 (c) 14 (d) 16

Answer: (b) 10 Mass number (A) of the atom = 27 Number of the neutron in the atom =14 Number of Electrons = Mass number - Number of neutrons... View Article

Rutherford’s α–particle scattering experiment showed that (i) electrons have negative charge (ii) the mass and positive charge of the atom is concentrated in the nucleus (iii) neutron exists in the nucleus (iv) most of the space in atom is empty Which of the above statements are correct? (a) (i) and (iii) (b) (ii) and (iv) (c) (i) and (iv) (d) (iii) and (iv

Answer: (b) (ii) and (iv) An atom consists of a positively charged, dense and very small nucleus which have all the protons and neutrons. The... View Article

In the Thomson’s model of atom, which of the following statements are correct? (i) the mass of the atom is assumed to be uniformly distributed over the atom (ii) the positive charge is assumed to be uniformly distributed over the atom (iii) the electrons are uniformly distributed in the positively charged sphere (iv) the electrons attract each other to stabilise the atom (a) (i), (ii) and (iii) (b) (i) and (iii) (c) (i) and (iv) (d) (i), (iii) and (iv)

Answer: (a) (i), (ii) and (iii) Thomson assumed that an electron is two thousand times lighter than a proton and believed that an atom is made... View Article

Which of the following are true for an element? (i) Atomic number = number of protons + number of electrons (ii) Mass number = number of protons + number of neutrons (iii) Atomic mass = number of protons = number of neutrons (iv) Atomic number = number of protons = number of electrons (a) (i) and (ii) (b) (i) and (iii) (c) (ii) and (iii) (d) (ii) and (iv)

Answer: (d) (ii) and (iv) Atomic number (Z) is the number of protons present in an electron which is also equal to a number of the electron in an... View Article

Which of the following statements about Rutherford’s model of atom are correct? (i) considered the nucleus as positively charged (ii) established that the α–particles are four times as heavy as a hydrogen atom (iii) can be compared to solar system (iv) was in agreement with Thomson’s model (a) (i) and (iii) (b) (ii) and (iii) (c) (i) and (iv) (d) only (i)

Answer:(a) (i) and (iii) Positively charged alpha particles were deflected by the nucleus. This shows the nucleus is positively charged.... View Article

Dalton’s atomic theory successfully explained (i) Law of conservation of mass (ii) Law of constant composition (iii) Law of radioactivity (iv) Law of multiple proportion (a) (i), (ii) and (iii) (b) (i), (iii) and (iv) (c) (ii), (iii) and (iv) (d) (i), (ii) and (iv)

Answer: (d) (i), (ii) and (iv) Dalton’s theory explains Law of conservation of mass, Law of constant composition, Law of multiple... View Article

The number of electrons in an element X is 15 and the number of neutrons is 16. Which of the following is the correct representation of the element? (a) ³¹ ₁₅ X (b)³¹ ₁₆X (c) ¹⁶ ₁₅ X (d) ¹⁵ ₁₆ X

Answer: (a) 3115 X Number of electrons = 15 Number of neutrons = 16 Number of protons in an element depicts atomic number. A number of protons... View Article

M	T	W	T	F	S	S
		1	2	3	4	5
6	7	8	9	10	11	12
13	14	15	16	17	18	19
20	21	22	23	24	25	26
27	28	29	30