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Atomic Foundations of Matter
NCERT Solutions
NCERT Solutions
Atomic Foundations of Matter
15 Solutions
Q1
Revise, Reflect, Refine
A particular element (A) has one electron in its third shell. There is another element (B) with six electrons in its second shell.
(i)
How many electrons does A tend to give or take to become stable?
(ii)
What kind of ion would it form?
(iii)
How many electrons does B tend to give or take to become stable?
(iv)
What kind of ion would it form?
(v)
If A and B were to combine, what kind of bond would be formed?
(vi)
What would be the formula for the compound thus formed?
Q2
Revise, Reflect, Refine
An element X has six electrons in its outer shell and forms a diatomic molecule.
(i)
Why would that be so?
(ii)
What kind of bond would it form?
(iii)
Draw the structure of the molecule it would form.
(iv)
A certain other element Y has two electrons in its second shell. Draw the structure of the molecule that X would form with Y.
Q3
Revise, Reflect, Refine
You want to design a new ionic compound, where the total positive charge is
6
+
6+
6
+
and the total negative charge is
6
−
6-
6
−
. Which of the following combinations gives the correct number of ions?
(i)
2
A
l
3
+
2 \, Al^{3+}
2
A
l
3
+
and
3
C
l
−
3 \, Cl^{-}
3
C
l
−
(ii)
3
M
g
2
+
3 \, Mg^{2+}
3
M
g
2
+
and
1
P
O
4
3
−
1 \, PO_{4}^{3-}
1
P
O
4
3
−
(iii)
2
F
e
3
+
2 \, Fe^{3+}
2
F
e
3
+
and
3
O
2
−
3 \, O^{2-}
3
O
2
−
(iv)
3
C
a
2
+
3 \, Ca^{2+}
3
C
a
2
+
and
2
S
O
4
2
−
2 \, SO_{4}^{2-}
2
S
O
4
2
−
Q4
Revise, Reflect, Refine
Choose the correct statement(s) and correct the false statement(s).
(i)
Elements are made up of molecules and compounds are made up of atoms.
(ii)
The molecule of a compound is always made up of two or more atoms of the same kind.
(iii)
One molecule of nitrogen gas contains three nitrogen atoms.
(iv)
Water is made of two hydrogen atoms, covalently bonded with one oxygen atom.
Q5
Revise, Reflect, Refine
Write the chemical formulae for the following compounds.
(i)
Aluminium nitrate
(ii)
Calcium oxide
(iii)
Ferric oxide
Q6
Revise, Reflect, Refine
Write the formulae of the compounds formed from the following pairs of ions.
(i)
C
a
2
+
Ca^{2+}
C
a
2
+
and
B
r
−
Br^{-}
B
r
−
(ii)
A
l
3
+
Al^{3+}
A
l
3
+
and
C
O
3
2
−
CO_{3}^{2-}
C
O
3
2
−
(iii)
K
+
K^{+}
K
+
and
S
O
4
2
−
SO_{4}^{2-}
S
O
4
2
−
(iv)
N
H
4
+
NH_{4}^{+}
N
H
4
+
and
C
l
−
Cl^{-}
C
l
−
Q7
Revise, Reflect, Refine
Which of the following, in Fig. 9.18, correctly represents
C
l
−
Cl^{-}
C
l
−
ion (Atomic number of chlorine = 17).
Q8
Revise, Reflect, Refine
Determine the formula unit mass of the following substances.
(i)
Ammonium nitrate (
N
H
4
N
O
3
NH_4NO_3
N
H
4
N
O
3
), used as a nitrogen fertiliser, which is essential for plant growth.
(ii)
Phosphoric acid (
H
3
P
O
4
H_3PO_4
H
3
P
O
4
), used to make phosphate fertiliser and detergents.
(iii)
Sodium hydrogencarbonate (
N
a
H
C
O
3
NaHCO_3
N
a
H
C
O
3
), used to relieve acidity and helps in digestion.
Q9
Revise, Reflect, Refine
Write the formulae for the compounds formed by the reaction of:
(i)
Magnesium and nitrogen
(ii)
Lithium and nitrogen
(iii)
Sodium and sulfur
(iv)
Aluminium and oxygen
Q10
Revise, Reflect, Refine
Complete the Table 9.3 by writing the formulae of the compounds formed by the cations on the left and the anions at the top.
L
i
N
O
3
LiNO_3
L
i
N
O
3
is given as an example.
N
O
3
−
NO_3^{-}
N
O
3
−
S
O
4
2
−
SO_4^{2-}
S
O
4
2
−
P
O
4
3
−
PO_4^{3-}
P
O
4
3
−
N
H
4
+
NH_4^{+}
N
H
4
+
L
i
+
Li^{+}
L
i
+
L
i
N
O
3
LiNO_3
L
i
N
O
3
A
l
3
+
Al^{3+}
A
l
3
+
C
u
2
+
Cu^{2+}
C
u
2
+
Q11
Revise, Reflect, Refine
5.3 g of sodium carbonate and 6.0 g of acetic acid react to produce 2.2 g of carbon dioxide, 0.9 g of water, and 8.2 g of sodium acetate. Verify whether the law of conservation of mass is valid.
Q12
Revise, Reflect, Refine
If a species has 11 protons, 12 neutrons and 10 electrons then
(i)
what is its atomic number and mass number?
(ii)
is it neutral, a cation or an anion? Explain.
(iii)
write its electronic configuration.
(iv)
name the species.
Q13
Revise, Reflect, Refine
Two elements, A and B, have the following configurations- A: 2, 8, 5 B: 2, 8, 7
(i)
Which element is more reactive?
(ii)
Will A and B form ionic or covalent bonds when they combine? Explain using electron transfer or sharing.
(iii)
Predict the formula of the compound they would form.
Q14
Revise, Reflect, Refine
Assertion (A): Copper sulfate conducts electricity in the molten state but not in the solid state. Reason (R): Copper and sulfate ions are fixed in the lattice in molten state, while in solid state they can move freely. Choose the correct option:
(i)
Both A and R are true, and R is the correct explanation of A.
(ii)
Both A and R are true, but R is not the correct explanation of A.
(iii)
A is true, but R is false.
(iv)
A is false, but R is true.
Q15
Revise, Reflect, Refine
The species
27
A
l
{}^{27}Al
27
A
l
,
80
B
r
−
{}^{80}Br^{-}
80
B
r
−
and
201
H
g
2
+
{}^{201}Hg^{2+}
201
H
g
2
+
have 13, 35 and 80 protons, respectively. How many electrons and neutrons do they have?
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