Question

18. The isotopes of neutral atoms of an element differ in 1) Atomic number 2) Mass number 3) Number of electrons 4) Chemical properties 19. The number of nucleons in the isotope of an atom z Xm are 1) m 2) Z 3) m+Z 4) m–Z 20. The constant of e/m ratio for electron shows that 1) Electron’s mass is 1/1837th of proton 2) Electrons are universal particles of all matter 3) Electrons are produced in discharge tubes only 4) None of the above

Answer 1

matter

Hope this answer is useful

Answer 2

The Main Answers are: 18.)  (2) Mass number

                                        19.) (1) m

                                        20.) (2) Electrons are universal particles of all matter

Explanation:

18.) (2) Mass number

• Isotopes are atoms of the same element which have the same atomic number but differ in mass number.

• This difference is due to the different number of neutrons in the isotopes.

• But, due to having the same atomic number, isotopes have similar chemical properties.

• Also, because of having the same no. of protons, i.e., same atomic no., isotopes also have the same no. of electrons.

19.) (1) m

• An atom can be symbolized in the following manner - $_{z}^{m}X$; where

       where z = atomic number,

       m = mass number, and

       X = chemical formula of the atom

• We know, mass number = no. of protons + no. of neutrons
• Also, all the protons and the neutrons are collectively called "nucleons".
• This is because they together comprise the nucleus of an atom.
• Therefore, here, m = no. of nucleons.

20.) (2) Electrons are universal particles of all matter

• The e/m ratio for an electron is the ratio of its charge and mass.
• For an electron, e/m = 1.758820 × $10^{11}$ C/kg.
• From experiments, it was concluded that when calculating the e/m value in a discharge tube, even on changing the gas in the tube, the value of the ratio remained constant.
• This shows that electrons are universal particles of all matter and their properties do not depend on the surrounding matter.

Therefore, the answers are: 18.)  (2) Mass number

                                                 19.) (1) m

                                                 20.) (2) Electrons are universal particles of all matter.

For similar questions on isotopes, refer to:

https://brainly.in/question/11843449?msp_srt_exp=6

https://brainly.in/question/2707089?msp_srt_exp=6

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