Structure of Atom MCQ Quiz - Objective Question with Answer for Structure of Atom - Download Free PDF

CONCEPT:

Periodic Groups and Their Properties

• Elements in the same group of the periodic table have similar chemical properties because they have the same number of valence electrons.
• Group 2 elements, also known as alkaline earth metals (e.g., Be, Mg, Ca, etc.), typically form compounds with the formula XCl₂, where X is the metal, and Cl is the chloride ion.
• These chlorides are ionic compounds that are generally solids with high melting points due to the strong electrostatic forces between the ions.

EXPLANATION:

• The formula of the chloride formed by element X is XCl₂, which suggests that X has a valency of +2.
• In the periodic table:
  • Na (sodium) belongs to Group 1 and forms NaCl, not XCl₂.
  • Al (aluminum) belongs to Group 13 and forms AlCl₃, not XCl₂.
  • Mg (magnesium) belongs to Group 2 and forms MgCl₂, which matches the formula XCl₂.
  • K (potassium) belongs to Group 1 and forms KCl, not XCl₂.

Since the formula XCl₂ is characteristic of Group 2 elements, X is most likely in the same group as magnesium (Mg).

Therefore, the correct answer is Mg.

CONCEPT:

Rutherford's Nuclear Model of Atom

• Rutherford conducted the gold foil experiment and proposed the nuclear model of the atom.
• The key features of Rutherford's model are:
  • An atom has a dense, positively charged nucleus at its center.
  • Nearly all the mass of the atom resides in the nucleus.
  • Electrons revolve around the nucleus in circular paths called orbits.
  • The size of the nucleus is very small compared to the size of the atom.

EXPLANATION:

• "There is a neutral centre in an atom called nucleus" — This is incorrect because the nucleus is positively charged due to protons, not neutral.
• "Nearly all the mass of an atom resides in the nucleus" — This is a correct observation from Rutherford's model.
• "The electrons revolve around the nucleus in a circular path" — This is also a correct observation according to Rutherford's model.
• "The size of a nucleus is very small as compared to the size of atom" — This is correct and is consistent with Rutherford's findings.

Therefore, the statement in Option 1 is NOT observed in Rutherford's Nuclear Model because the nucleus is positively charged, not neutral.

CONCEPT:

Discovery of the Neutron

• In 1932, James Chadwick discovered the neutron, a subatomic particle present in the nucleus of an atom.
• The neutron is electrically neutral, meaning it has no charge, and its mass is almost equal to that of a proton.
• Chadwick's discovery was essential in understanding the atomic nucleus and led to advancements in nuclear physics, including nuclear fission and the development of atomic energy.

EXPLANATION:

• Before Chadwick's discovery, the nucleus of an atom was thought to consist only of protons.
• However, the atomic mass of many elements was found to be higher than what could be explained by the number of protons alone.
• Chadwick conducted experiments by bombarding beryllium with alpha particles, which resulted in the emission of a neutral radiation that could not be explained by existing theories.

He concluded that this radiation consisted of previously unknown particles, which he named neutrons.

Therefore, the particle in the nucleus of an atom discovered by J. Chadwick is the neutron.

The correct answer is 256 u.

Key Points

• The atomic mass of sulphur is 32 u.
• Sulphur exists as S₈ molecules.
• To find the molecular mass of sulphur, multiply the atomic mass of sulphur by the number of atoms in one molecule of sulphur.
• Calculation: 32u×8=256u" id="MathJax-Element-1-Frame" role="presentation" style="position: relative;" tabindex="0">32u×8=256u32u×8=256u $32 \, \text{u} \times 8 = 256 \, \text{u}$
• Thus, the molecular mass of sulphur is 256 u.

 Additional Information

• Atomic Mass Unit (u)
  • An atomic mass unit (u) is a standard unit of mass that quantifies mass on an atomic or molecular scale.
  • It is defined as one-twelfth of the mass of an unbound atom of carbon-12 at rest and in its ground state.
• Molecular Mass
  • The molecular mass (or molecular weight) is the mass of a given molecule and is calculated as the sum of the atomic masses of the atoms in the molecule.
  • It is typically measured in atomic mass units (u).

The correct answer is Hydrogen.

Key Points

• Neutrons are present in the nucleus of all atoms, except hydrogen.
• Hydrogen is the lightest element. 
• It exists as the stable isotope Deuterium and the unstable, radioactive isotope Tritium.
• Hydrogen (H) is a colourless, odourless, tasteless, flammable gas.
• It is the simplest chemical element.
• The hydrogen has a nucleus consisting of a proton bearing one unit of positive electrical charge, and an electron, bearing one unit of negative electrical charge, is also associated with this nucleus, but no neutron.
• It exists as a diatomic molecule, H₂.

• The word ‘atom’ is coined by Democritus.
• He suggested that if we go on dividing matter at a certain point the atom becomes indivisible or cannot be divided further.
• He called these particles as atoms (Indivisible).

 

Scientist	Discovered
Thomson	Electron
E Rutherford	Discovered alpha and beta particles
John Dalton	Father of Atomic Theory

• Group 1 elements in the Periodic table are known as Alkali metals
• They have ns1 outermost configuration and belong to the S-block Elements.
• They also have a strong tendency to donate their valence electrons in the outermost shell to form strong ionic bonds.
• It contains elements from Lithium (Li) to Francium (Fr).

The correct answer is Phosphorous.

Key Points

• The present number of atoms in any molecule of an element is called its atomicity.
• Tetra atomic elements are those which are made up of four atoms. 
• Phosphorous exists as molecules made up of four atoms in a tetrahedral structure.
• Each phosphorus molecule consists of four atoms of phosphorus.

Important Points

• The following table shows the atomicity of some elements. 

• Electron Shell (also called a Principle energy level) is the region where electrons revolve around the nucleus of an atom.
• The general formula of filling electron in the shell is 2(n²); where n is the number of the shell.

SHELL	n	2(n2)	SHELL MAXIMUM ELECTRON
K	1	= 2(12)	2
L	2	= 2(22)	8
M	3	= 2(32)	18
N	4	= 2(42)	32
O	5	= 2(52)	50

The correct answer is option 1, i.e. Fluorine.

• Fluorine is the most electronegative element.
• As we move right in a period, the electronegativity keeps increasing up to the halogens.
• This is because the number of electrons keeps increasing in the same valence shell so hold of the nucleus on the electrons is tight.
• And as we move down in a group, the electronegativity decreases. This is due to the fact that the number of shells keeps increasing down the group so the hold of the nucleus on the valence electron(s) keeps decreasing.
• Since Flourine is the first member of the halogen family (the rightmost group before noble gases), therefore it is the most electronegative element.

• Newlands Law of Octaves classification attempted to arrange elements by the atomic weight
• According to Newlands Law of Octaves classification, the eighth element starting from the given one kind is a repetition of the first element in the given kind
• This is similar to the property of musical notes
•  The eighth element would have similar atomic weight as that of the first one
• In this way, Thorium was the last element in the Newlands Law of Octaves classification

• Atomic number 56, Barium belongs to s - block elements.
• Electronic configuration for the Barium [Xe]6s²
• Modern Periodic Table is classified into the following elements - p-block, s-block, d-block, and f-block.
• s-block elements include alkali metals and alkaline earth metals.

 

The correct answer is helium.

Key Points

• Alpha Particle
  • α-particles consist of two protons and two neutrons.
  • They are doubly-charged helium ions. Since they have a mass of 4 u, the fast-moving α-particles have considerable energy.
  •  An alpha particle is obtained by removing 2 electrons from a helium atom. So, an alpha particle is a doubly-charged helium ion.
•  Helium:
  • Helium is a chemical element with the symbol He and atomic number 2.
  • It is a colourless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table.
  •  Its boiling and melting point are the lowest among all the elements.
  • It is the second lightest and most abundant element in the observable universe (hydrogen is the lightest and most abundant).

Additional Information

• Lithium
  • ​Lithium is a chemical element with the symbol Li and atomic number 3.
  • It is a soft, silver-white metal belonging to the alkali metal group of chemical elements.
• ​Beryllium
  • Beryllium is very similar to Aluminium.
  • Beryllium is soft and has a low density.
  • It is used in gears and in alloys with copper or nickel.
  • Beryllium is used in Nuclear Reactors.
  • Oxides of Beryllium have a high melting point.
• Hydrogen​
  • Hydrogen was discovered by Henry Cavendish.
  • Hydrogen gas is called as the fuel of the future.
  • Most abundant element in the universe: Hydrogen.
  • Most abundant element on earth's crust: Oxygen
  • Hydrogen is the 'lightest element' in the periodic table.
  • Lithium is the 'lightest metal' in the periodic table.

The correct answer is option 3, i.e. John Dalton.