This law states that "The physical and chemical properties of elements are a periodic function of their atomic weights."

The total pressure of a mixture of gases is the sum of partial pressures of the gases present. Partial pressure of a gas is the pressure exerted by the gas when it is present alone in that volume.

H₂ = 1 + 1 = 2e^-
H⁺₂; = 2 - 1 = le^-
\({O}_{2}\) = 8 + 8 = 16e^-
\({O}_{2}^{-}\) = 8 + 8 + 1= 17e^-

It is defined as the imaginary charge left on the atom when all other atoms of the compound have been removed in their usual oxidation states that are assigned according to set of rules.

According to Charles' law,
\(\frac{V_1}{T_1}=\frac{V_2}{T_2}=\frac{V_3}{T_3}\)
\(\frac{0.3dm^3}{200K}=\frac{V_2}{300K}=\frac{0.15dm^3}{T_3}\)
\(\frac{V_2}{300K}=\frac{0.3dm^3}{200K}\)

V₂ = 0.45 dm³ and
\(\frac{0.15dm^3}{T_3}=\frac{0.3dm_3}{200K}\)

T₃ = 100 K.

The elements in which extra electron enters (n-2) f-orbitals are called f-block elements. These elements form a transition series within the transition elements. So these elements are called inner transition elements.

1 x AW of Na = 1 x 22.99 = 22.99 amu
1 x AW of O = 1x 16 = 16.00 amu
1 x AW of H = 1 x1.008 = 1.008 amu
Formula weight of NaOH is = 39.998 amu

1) The unit of molecular mass is atomic mass unit [amu]. The unit of molar mass is gram per mole.
2) Molecular mass is the mass of one molecule while molar mass is the mass of one mole of molecules (6.022 x 10²³)
(i) Molecular mass of CO₂ = 1(C) + 2(0) = 12 + 32 = 44 amu
or 7.304 x 10^-23 g
(ii) Molar mass of CO₂ = 44 g mol^-1.

De Broglie wavelength of the tennis ball equal to 5400 \(\overset { 0 }{ A } \).
m = 54 g 
V = ?
\(\lambda=\frac{h}{mV}\)
\(V=\frac{h}{m\lambda}\)
\(\mathrm{v}=\frac{6.626 \times 10^{-34} \mathrm{JS}}{54 \times 10^{-3} \mathrm{~kg} \times 5400 \times 10^{-10} \mathrm{~m}}=2.27 \times 10^{-26} \mathrm{~ms}^{-1}\)

The number of electrons in an atom of an element is 19.
The electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
The total number of p-orbitals for the element is 2p level- 3 and 3p level- 3. i.e. '6' orbitals.

Merits of Moseley's long form of periodic table:
(i) As this classification is based on atomic number, it relates the position of an element to its electronic configuration.
(ii) The elements having similar electronic configuration fall in a group. They also have similar physical and chemical properties.
(iii) The completion of each period is more logical. In a period as the atomic number increases, the energy shells are gradually filled up until an inert gas configuration is reached.
(iv) The position of zero group is also justified in the table as group 18.
(v) The table completely separates metals and non-metals.
(vi} The table separates two subgroups, lanthanides and actinides, dissimilar elements do not fall together.
(vii) The greatest advantage of this periodic table is that this can be divided into four blocks namely s, p, d and f-block elements.
(viii) This arrangement of elements is easier to remember, understand and reproduce.

Volume of the gas in the balloon V₁ = 400 ml
temperature T₁ = -120 °C + 273
= 153 K
If the balloon is warmed T₂  = 100° C + 273
to a temperature = 373 K
Then the volume of the gas V₂ = ?
According to charles law \(\frac { { V }_{ 1 } }{ { T }_{ 1 } } =\frac { { V }_{ 2 } }{ { T }_{ 2 } } \)
\({ V }_{ 2 }=\frac { { V }_{ 2 } }{ { T }_{ 1 } } \times { T }_{ 2 }\)
\(=\frac { 400 }{ 153 } \times 373=975\quad ml\)
\(\therefore\)   Volume of helium gas in the balloon at a temperature of 100°C = 975 ml

(i)	Atomic Mass	Molecular Mass
	Atomic mass is the mass of a single atom,  which is its collective mass of neutron proton and electrons	Molecular weight is the mass of one molecule Molecular mass can be calculated from the sum of atomic masses of all atoms present in a compound.
(ii)	Atomic Mass	Atomic Mass
	Atomic mass is the mass of a single atom,  which is its collective mass of neutron, proton and electrons	Atomic weight is the average weight of an elements with respect to all its isotopes and their relative abundance.
(iii)	Empricial Formula	Molecular Formula
	It represents the simplest whole number ratio of various atoms present in one molecule of the compound. Empirical formula of Benzene is CH	The molecular formula shows the exact number of different types of atoms present in  a molecule of a compound.  Molecular formula of Benzene is C6H6.
(iv)	Moles	Molecules
	The amount of the substance that contains specified particles as the number of atoms in 12 g carbon - 12 isotope	Two or more atoms joint together by chemical bonds.

2Al + Fe₂O₃ \(\longrightarrow \)  Al₂O₃ + 2Fe

	Reactants		Products
	Al	Fe2O3	Al2O3	Fe
Amount of reactant allowed to react	324 g	1.12 kg	-	-
Number of moles allowed to react	\(\frac { 324 }{ 27 } =12mol\)	\(\frac { 1.12\times { 10 }^{ 3 } }{ 160 } =7mol\)	-	-
Stoichiometric Co-efficient	2	1	1	2
Number of moles consumed during reaction	12 mol	6 mol	-	-
Number of moles of reactant unreacted and number of moles of product formed	-	1 mol	6 mol	12 mol

Molar mass of Al₂O₃ format = 6 mol x 102 g mol^-1 = 612 g
[  Al₂O₃ : (2 x 27) + 3(16) = 54 + 48 = 102] = 612 g
Excess reagent = Fe₂O₃
Amount of excess reagent left at the end of the reaction = 1 mol x 160 g mol^-1
= 160g [ Fe₂O₃ : (2 x 56) + (3 x 16) = 112 + 48 = 160] = 160 g

(c) Assertion is true and the reason is false