Atoms with the same atomic number and different mass number are called ____.

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Atoms with the same atomic number and different mass number are called as isotopes. E.g. 12C, 13C are isotopes of carbon having mass numbers of 12 and 13 respectively. Atomic number of carbon is 6 for both.

Atoms with same mass number and different atomic number are ____.

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Atoms with same mass number and different atomic number are isobars. E.g. 14C, 14N- Here, carbon and nitrogen have the same mass number, but the atomic number of carbon is 6 and that of nitrogen is 7. So, this pair is called isobars.

The stability of half-filled orbitals are due to____.

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The stability of half-filled orbitals is due to symmetrical distribution of electrons and exchange energy. If orbital is in half-filled position, there is a symmetry in the molecule, which leads to more stability of the molecule.

The number of protons in the nucleus of an atom is equal to the ____.

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The number of protons in the nucleus of an atom is equal to the number of electrons in the neutral atom. In positive or negatively charged ions, the number of protons will not be equal to that of electrons. The number of protons will be either less or more.

The difference between isotopes is due to the presence of different number of ____ present in it.

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The difference between isotopes is due to the presence of different number of neutrons present in it. In isotopes, the atomic number of the elements is the same, but mass number is different. This mass number difference is due to the presence of neutrons in it.

In the symbolic representation of an atom, mass number is represented ____.

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In any atom, mass number is represented as superscript on the left side of the symbol. Atomic number is represented in subscript, e.g. 1H means mass number of proton is one. 1H means atomic number is one.

The principle of cathode ray tubes is applied in ____.

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The principle of cathode ray tubes is applied in television picture tubes. Television pictures are due to fluorescence on the television screen that is coated with certain fluorescent or phosphorescent materials.

Presence of two electrons in valence shell of atom of element is calls ____ configuration.

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Presence of two electrons in the valence shell of atom of an element is called duplet configuration.

The distribution of electrons in degenerate orbital’s as in 1s2 2s2 2px12py12pz1 can be explained on the basis of ____.

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The electronic configuration of 1s2 2s2 2px12py12pz1 can be explained on the basis of Hund's rule of maximum multiplicity. The rule says that “in a set of degerate orbital’s, first the orbital’s are singly occupied and then the pairing of electrons takes place".

Sub-atomic particles electron and neutron were discovered by ____ and ____ respectively.

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Sub-atomic particles of electron and neutron were discovered by J. J. Thomson & Chadwick respectively. Sub-atomic particles are the particles which are present in the atom viz., electrons, neutrons and protons.

Neutrons present in the atom have very little effect on the ____ properties.

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Neutrons present in the atom have very little effect on the chemical properties of the atom. All chemical properties of an atom are controlled by the electrons present in the atom.

The atomic number of the atom is equal to the number of ____present in the nucleus.

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The atomic number of the atom is equal to the number of protons present in the nucleus.

The number of unpaired electrons in the Fe3+ion is____.

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The unpaired electrons in the Fe3+ ion is 5. The electronic configuration of Fe is [Ar] 3d64s2. EC of Fe3+ becomes [Ar] 3d5. This shows the presence of 5 unpaired electrons in the 3d orbitals.

____ group in the periodic table having minimum energy.

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We Know Energy and stability are inversely related .Zero group elements are highly stable due to their stable electronic configuration. As zero group elements stability is maximum, energy is minimum.

The electronic configuration of boron is ____.

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The electronic configuration of boron is 1s2 2s2 2p1. Atomic number of boron is 5. So, its electronic configuration is 1s2 2s2 2p1.

The advantage of expressing electronic configuration is that it gives an idea about ____.

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The advantage of expressing electronic configuration in orbital form is that it gives an idea about the chemical behaviour of the elements. The valence shell configuration of the elements predicts the chemical behaviour of the elements.

The total number of protons and neutrons is equal to the ____ of an atom.

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The total number of protons and neutrons is equal to the mass number of an atom. Protons and neutrons present in the nucleus are collectively known as nucleons.

The number of protons and neutrons present in tritium an isotope of hydrogen are ____ respectively.

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The number of protons and neutrons present in tritium an isotope of hydrogen are 1 and 2 respectively. Since tritium is an isotope of hydrogen, its atomic number is one. But mass number of tritium is 3 (protons + neutrons). So, 3 - 1 = 2 The number of protons (equal to atomic number) is 1 and the number of neutrons is 2.

The release of ____ leads to the extra stability of the half-filled or completely-filled configurations.

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The release of exchange energy leads to the extra stability of half-filled or completely-filled configurations. According to the number of electrons, orbital’s themselves exchange their electrons in the degenerate orbital’s (orbital’s having equal energy) to attain either half-filled or completely filled configuration. During this exchange, some energy is released. This is called exchange energy, which leads to more stable molecules.

The number of electron(s) lost , gained or shared by atom of an element to form a chemical bond to attain stable electronic configuration is called ____.

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The number of electrons lost, gained or shared by atom of an element to form a chemical bond is called valency. In the formation of NaCl, sodium lost one electron and chlorine gains one electron. So, the valency of sodium and chlorine is one.

The electrons in the completely filled shells are called as____.

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The electrons in the completely filled shells are called as core electrons. For eg. Sodium has the atomic number 11. Electronic configuration for sodium is 1s2 2s2 2p6 3s1. Here, first (1s2) and second shells (2s2 2p6) are completely filled and the third shell is incomplete. The electrons in the completed shells are known as core electrons and the electrons in the incomplete shells are known as valence electrons.

Atoms like oxygen and chlorine ____ the electrons to form stable molecules such as O2 and Cl2.

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Atoms like oxygen and chlorine shares the electrons to form molecules such as O2 and Cl2.

In the formation of sodium chloride, ____loses the electron(s) to attain stable electronic configuration of ____.

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In the formation of sodium chloride, sodium loses one electron to attain stable electronic configuration of neon i.e. 2, 8.

In the Cathode ray discharge tube current flows only at ____.

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Cathode ray discharge tube current flows only in partially evacuated tubes that is at low pressures.

All the ____ of a given element have same chemical properties.

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All the isotopes of a given element have same chemical properties. Since isotopes differ only in number of neutrons, there is no much difference in its chemical properties.

ICSE Class 9th Chemistry 4 - Atomic structure and chemical bonding MCQs
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