Molecules and Ions Questions in English

(A) $(i)$ In a $H_2S$ molecule,there are $2$ atoms of hydrogen and $1$ atom of sulphur.
Total atoms = $2 + 1 = 3$ atoms.
$(ii)$ In a $PO_4^{3-}$ ion,there is $1$ atom of phosphorus and $4$ atoms of oxygen.
Total atoms = $1 + 4 = 5$ atoms.

(N/A) polyatomic ion is a group of atoms carrying a fixed net charge (either positive or negative) that behaves as a single unit during chemical reactions.
Examples:
$(i)$ Carbonate ion: $CO_3^{2-}$
$(ii)$ Sulphate ion: $SO_4^{2-}$
$(iii)$ Ammonium ion: $NH_4^+$
$(iv)$ Phosphate ion: $PO_4^{3-}$

(N/A) Two biologically important compounds that contain both oxygen and nitrogen are amino acids and nucleic acids ($DNA$ and $RNA$). Amino acids are the building blocks of proteins and contain an amino group $(-NH_2)$ and a carboxyl group $(-COOH)$. Nucleic acids contain nitrogenous bases,sugars,and phosphate groups,all of which involve both nitrogen and oxygen atoms.

(C) Nitrogen gas exists as a diatomic molecule in nature. Therefore,its chemical formula is represented as $N_2$.

(N/A) To identify the ions, we look at the dissociation of ionic compounds in an aqueous solution. Covalent compounds do not dissociate into ions.

Compound	Cation	Anion
$(a)$ $CH_3COONa$	$Na^+$	$CH_3COO^-$
$(b)$ $NaCl$	$Na^+$	$Cl^-$
$(c)$ $H_2$	None (Covalent)	None (Covalent)
$(d)$ $NH_4NO_3$	$NH_4^+$	$NO_3^-$

(A) $CO_{3}^{2-}$ consists of $1$ carbon atom and $3$ oxygen atoms,totaling $1 + 3 = 4$ atoms.
$(b)$ $PO_{4}^{3-}$ consists of $1$ phosphorus atom and $4$ oxygen atoms,totaling $1 + 4 = 5$ atoms.
$(c)$ $P_{2}O_{5}$ consists of $2$ phosphorus atoms and $5$ oxygen atoms,totaling $2 + 5 = 7$ atoms.
$(d)$ $CO$ consists of $1$ carbon atom and $1$ oxygen atom,totaling $1 + 1 = 2$ atoms.

(N/A) Atomicity is the total number of atoms present in one molecule of an element or compound.
$(a) F_2$: Diatomic ($2$ atoms)
$(b) NO_2$: Triatomic ($3$ atoms)
$(c) N_2O$: Triatomic ($3$ atoms)
$(d) C_2H_6$: Octatomic ($8$ atoms)
$(e) P_4$: Tetratomic ($4$ atoms)
$(f) H_2O_2$: Tetratomic ($4$ atoms)
$(g) P_4O_{10}$: Polyatomic ($14$ atoms)
$(h) O_3$: Triatomic ($3$ atoms)
$(i) HCl$: Diatomic ($2$ atoms)
$(j) CH_4$: Pentatomic ($5$ atoms)
$(k) He$: Monoatomic ($1$ atom)
$(l) Ag$: Polyatomic (Metals exist as a giant lattice structure containing a large number of atoms).

(A) $Mg^{2+}$ ion and a $Mg$ atom differ by two electrons.
$10^{3} \, \text{mol}$ of $Mg^{2+}$ ions and $Mg$ atoms would differ by $10^{3} \times 2 \, \text{mol}$ of electrons.
Number of electrons $= 2 \times 10^{3} \times 6.022 \times 10^{23} = 12.044 \times 10^{26} \, \text{electrons}$.
Mass of $2 \times 10^{3} \, \text{mol}$ of electrons $= 2 \times 10^{3} \times 6.022 \times 10^{23} \times 9.1 \times 10^{-31} \, \text{kg}$.
$= 12.044 \times 10^{26} \times 9.1 \times 10^{-31} \, \text{kg}$.
$= 109.6004 \times 10^{-5} \, \text{kg}$.
$= 1.096 \times 10^{-3} \, \text{kg}$.

(A) The molar mass of $NaCl$ is $23 + 35.5 = 58.5 \, g/mol$.
Number of moles of $NaCl = \frac{\text{Given mass}}{\text{Molar mass}} = \frac{5.85 \, g}{58.5 \, g/mol} = 0.1 \, mol$.
Each formula unit of $NaCl$ dissociates into two ions: one $Na^+$ ion and one $Cl^-$ ion.
Therefore,total moles of ions $= 0.1 \, mol \times 2 = 0.2 \, mol$.
Number of ions $= \text{Moles of ions} \times \text{Avogadro constant}$.
Number of ions $= 0.2 \times 6.022 \times 10^{23} = 1.2044 \times 10^{23}$ (approximately $1.2042 \times 10^{23}$ based on standard calculation).
Thus,the correct option is $A$.

(N/A) Molecular compounds are formed when atoms of different elements combine in definite proportions to form molecules. Examples include $H_2O$ (water),$NH_3$ (ammonia),and $CO_2$ (carbon dioxide).
Ionic compounds are composed of metals and non-metals containing charged species known as ions. An ion is a charged particle,which can be either positively charged (cation) or negatively charged (anion). Examples include $NaCl$ (sodium chloride) and $CaO$ (calcium oxide).

(N/A) $(i)$ Cation: $Al^{3+}$ (Aluminium ion)
$(ii)$ Anion: $O^{2-}$ (Oxide ion)

(N/A) Atomicity is defined as the total number of atoms present in one molecule of an element.
$(i)$ The chemical formula of a sulphur molecule is $S_{8}$. Since it contains $8$ atoms of sulphur,its atomicity is $8$ (Polyatomic).
$(ii)$ The chemical formula of a phosphorus molecule is $P_{4}$. Since it contains $4$ atoms of phosphorus,its atomicity is $4$ (Tetraatomic).

(N/A) Atomicity is defined as the total number of atoms present in one molecule of a substance.
$(i)$ In $H_{2}SO_{4}$ (Sulfuric acid):
Number of Hydrogen atoms = $2$
Number of Sulfur atoms = $1$
Number of Oxygen atoms = $4$
Total atoms = $2 + 1 + 4 = 7$
Therefore,the atomicity is $7$.
$(ii)$ In $CCl_{4}$ (Carbon tetrachloride):
Number of Carbon atoms = $1$
Number of Chlorine atoms = $4$
Total atoms = $1 + 4 = 5$
Therefore,the atomicity is $5$.

(N/A) $2H$ represents $2$ individual atoms of hydrogen,which exist independently. In contrast,$H_2$ represents a single molecule of hydrogen,which consists of $2$ hydrogen atoms chemically bonded together.

(C) polyatomic ion is an ion composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit.
$1$. In $NaOH$,the hydroxide ion $(OH^-)$ is a polyatomic ion.
$2$. In $NaCl$,both $Na^+$ and $Cl^-$ are monatomic ions.
$3$. In $Na_{2}O$,both $Na^+$ and $O^{2-}$ are monatomic ions.
$4$. In $NaNO_{3}$,the nitrate ion $(NO_{3}^-)$ is a polyatomic ion.
Therefore,$NaOH$ and $NaNO_{3}$ contain polyatomic ions.

(N/A) $O_3$ (Ozone) is a triatomic element because it consists of three oxygen atoms.
$(b)$ $Ar$ (Argon) is a monoatomic molecule as it is a noble gas and exists as a single atom.
$(c)$ $S_8$ (Sulphur) is a polyatomic element because its molecule consists of eight sulphur atoms.
$(d)$ $SO_4^{2-}$ (Sulphate) or $NH_4^+$ (Ammonium) are examples of polyatomic ions,which are ions consisting of more than one atom.

(N/A)

Cation	Anion
$1.$ It is positively charged,e.g.,$Na^+$	$1.$ It is negatively charged,e.g.,$Cl^-$
$2.$ It is formed from metal atoms.	$2.$ It is formed from non-metal atoms.
$3.$ On passing electric current,it moves towards the cathode.	$3.$ On passing electric current,it moves towards the anode.
$4.$ It is smaller in size than its parent atom.	$4.$ It is larger in size than its parent atom.

(N/A) Atomicity is defined as the total number of atoms present in one molecule of an element or a compound.
$(b)$ Monoatomic molecule: $He$ (Helium) or $Ne$ (Neon) are examples of monoatomic molecules because they consist of a single atom.
Polyatomic molecule: $S_8$ (Sulphur) is an example of a polyatomic molecule because it consists of eight atoms.

(B) The chemical formula of the sulfate ion is $SO_{4}^{2-}$.
This ion consists of one sulfur $(S)$ atom and four oxygen $(O)$ atoms.
Total number of atoms = $1$ (sulfur) + $4$ (oxygen) = $5$ atoms.
Therefore,the total number of atoms present in one $SO_{4}^{2-}$ ion is $5$.

(N/A) Ions are more stable than atoms because,except for the atoms of inert gases,the outermost shell of most atoms is incomplete. To achieve a stable electronic configuration (octet),atoms lose,gain,or share electrons to form ions.
$(b)$ The outermost shell of the atoms of noble gases is already complete (stable octet or duplet). Therefore,they have no tendency to lose,gain,or share electrons,resulting in low chemical reactivity.

(N/A) Atomicity is defined as the total number of atoms present in one molecule of an element or a compound.
$(b)$ The atomicity of the given molecules is as follows:
$(i)$ Oxygen $(O_2)$: Diatomic (contains $2$ atoms).
$(ii)$ Phosphorus $(P_4)$: Tetra-atomic (contains $4$ atoms).
$(iii)$ Sulphur $(S_8)$: Polyatomic (contains $8$ atoms).
$(iv)$ Argon $(Ar)$: Monoatomic (contains $1$ atom).

(N/A) The number of atoms present in one molecule of a substance is called its atomicity.
Depending on the number of atoms present in a molecule,the following types of molecules are known:
$(i)$ Monoatomic molecules: These consist of a single atom. Noble gases like $He$,$Ne$,and $Ar$ exist as monoatomic molecules.
$(ii)$ Diatomic molecules: These consist of two atoms,e.g.,$O_{2}$,$N_{2}$,$Cl_{2}$,$H_{2}$,$Br_{2}$,and $I_{2}$.
$(iii)$ Triatomic molecules: These consist of three atoms,e.g.,$O_{3}$ (Ozone molecule).
$(iv)$ Tetratomic molecules: These consist of four atoms,e.g.,$P_{4}$ (Phosphorus molecule).
$(v)$ Polyatomic molecules: These consist of more than four atoms,e.g.,$S_{8}$ (Sulphur molecule).
Note: All the above types represent molecules of an element,where atoms of the same element exist together as a single species in a free state.

(A) To find the number of molecules in a given amount of substance,we use Avogadro's number $(N_A = 6.022 \times 10^{23} \text{ molecules/mole})$.
The formula is: $\text{Number of molecules} = \text{Number of moles} \times N_A$.
Given,number of moles = $0.5$.
Therefore,$\text{Number of molecules} = 0.5 \times 6.022 \times 10^{23}$.
$= 3.011 \times 10^{23} \text{ molecules}$.

(B) Atomicity is defined as the total number of atoms present in one molecule of an element or compound.
$1$. Sulphur $(S_8)$ has an atomicity of $8$.
$2$. Phosphorus $(P_4)$ has an atomicity of $4$.
$3$. Ozone $(O_3)$ has an atomicity of $3$.
$4$. Methane $(CH_4)$ has an atomicity of $5$ ($1$ carbon atom + $4$ hydrogen atoms).
Therefore,the molecule with an atomicity of $4$ is the Phosphorus molecule.

(D) Nitrogen gas exists as a diatomic molecule in nature.
This means that two atoms of nitrogen are chemically bonded together to form a stable molecule.
Therefore,the chemical formula for nitrogen gas is represented as $N_{2}$.

(B) The statement is False.
Oxygen primarily exists in two allotropic forms in nature: dioxygen $(O_{2})$ and ozone $(O_{3})$.
While $O_{4}$ (oxozone) has been theoretically proposed and observed under extreme high-pressure conditions in laboratory settings,it is not considered a standard or stable form of oxygen molecule under normal atmospheric conditions.

(TRUE) The statement is True.
Iron $(Fe)$ is a transition metal that exhibits variable valency.
It can lose two electrons to form the ferrous ion $(Fe^{2+})$ or three electrons to form the ferric ion $(Fe^{3+})$.

(B) The statement is False.
$A$ group of atoms carrying a charge is known as a polyatomic ion,not a bivalent ion.
$A$ bivalent ion refers to an atom or ion that has a valency of $2$,meaning it can form two chemical bonds (e.g.,$Mg^{2+}$ or $Ca^{2+}$).

(B) The statement is False.
The atomicity of phosphorus $(P_4)$ is $4$,not $5$.
The atomicity of sulphur $(S_8)$ is $8$,not $6$.

(TRUE) The statement is True.
According to Avogadro's Law,one mole of any ideal gas at Standard Temperature and Pressure $(STP)$ occupies a volume of $22.4$ litres.
$STP$ is defined as a temperature of $0^{\circ} C$ $(273.15 \ K)$ and a pressure of $1$ atmosphere $(101.325 \ kPa)$.