Question

ASSERTION AND REASONING TYPE QUESTIONS FOR CLASS 9 NCERT CHEMISTRY:STRUCTURE OF ATOM.ATLEAST 10 QUESTION​

Answer 1

Answer:

1] Assertion (A) : Electron gain enthalpy becomes less negative as we go down a group.

Reason (R) : Size of the atom increases on going down the group and the added electron would be farther from the nucleus.

2] Assertion (A) : Boron has a smaller first ionisation enthalpy than beryllium.

Reason (R) : The penetration of a 2s electron to the nucleus is more than the 2p electron hence  2p electron is more shielded by the inner core of electrons than the 2s electrons.

3] Assertion (A) : Generally, ionization enthalpy increases from left to right in a period.

Reason (R) : When successive electrons are added to the orbitals in the same principal  quantum level, the shielding effect of inner core of electrons does not increase very much  to compensate for the increased attraction of the electron to the nucleus.

4] Assertion: The atoms of different elements having same mass number but different atomic number are known as isobars.

Reason: The sum protons and neutrons in isobars is always different.

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Answer 2

Explanation:

this is assertion and re