(i) Calculate the total number of electrons present in one mole of methane. (ii) Find (a) the total number and (b) the total mass of neutrons in 7 mg of \$\displaystyle ^{ 14 }{ C }\$.(Assume that mass of a neutron =\$\displaystyle 1.675\times { 10 }^{ -27 }kg\$).(iii) Find (a) the total number and (b) the total mass of protons in 34 mg of \$\displaystyle { NH }_{ 3 }\$ at STP.Will the answer change if the temperature and pressure are changed?

(i) Total number of electrons present in 1 methane molecule \$\displaystyle =6+4=10\$.Total number of electrons resent in 1 mole of methane \$\displaystyle = 10 \times 6.023 \times 10^{23} = 6.023 \times 10^{24}\$ electrons.The number of neutrons is equal to the difference in the mass number and atomic number.It is equal to \$\displaystyle 14-6=8 \$.(ii)(a) The number of neutrons present in 7 mg of C-14 is \$\displaystyle \frac {6.023 \times 10^{23} \times 8}{14} \times 7 \times 10^{10-3} = 2.4088 \times 10^{21}\$ neutrons.(b) Total mass of neutrons in 7 mg of C-14 is \$\displaystyle 2.4088 \times 10^{21} \times 1.675 \times 10^{-27} 4.035 \times 10^{-6}\$ kg.(iii)(a)Number of protons present in 1 molecule of ammonia \$\displaystyle =7+3=10 \$.Number of molecules present in 34 mg of ammonia is \$\displaystyle \frac {6.023 \times 10^{23} \times 34 \times 10^{-3}}{17} = 1.2044 \times 10^{21}\$.Total number of protons present in 34 mg of ammonia\$\displaystyle= 10 \times 1.2044\times 10^{21} = 1.2044\times 10^{22}\$(b) Total mass of protons present in 34 mg of ammonia at STP is \$\displaystyle 1.6726\times 10^{-27} \times 1.204 \times 10^{22} = 2.0138 \times 10^{-5} \$ kg.When temperature and pressure are changed, there is no difference in the answer.

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>>Structure of Atom
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Subatomic Particles - Comparison

Q: Which of the following statements is false?

The e/m value of electron is approximately \$1837\$ times e/m value of proton, hence e/m value of proton is not highest. Thus the false statement is present in option C. Thus answer is option C.

Q: If \$N_{A}\$ is Avogadro's number, then number of valence electrons in 4.2 g of nitride ion \$\left ( N^{3-} \right )\$ is:

Number of moles \$=\dfrac { 4.2 }{ 14 } =0.3\$ mol\$0.3\$ mol \$=0.3\times { N }_{ A }\$ ions.\$\Rightarrow 8\times 0.3\times { N }_{ A }\$ electrons (as each ion contains \$5+3={ 8e }^{ - }\$)\$\Rightarrow 2.4{ N }_{ A }\$ electronsHence, the correct option is A.

Q: (i) Calculate the number of electrons which will together weighs one gram. (ii) Calculate the mass and charge of one mole of electrons.

The number of electrons which will weigh 1 g is \$\displaystyle \frac {10^{-3}}{9.11 \times 10^{-31}} = 1.098 \times 10^{27} \$ .Mass of one mole of electrons is \$\displaystyle 9.11 \times 10^{-31} \times 6.023 \times 10^{23}= 5.486 \times 10^{-7} \$kg.Charge of 1 mole of electrons is \$\displaystyle 1.602 \times 10^{-19} \times 6.023\times 10^{23} = 9.647\times 10^{4}\ C\$.

Q: An element with mass number \$81\$ contains \$31.7\%\$ more neutrons as compared to protons. Assign the atomic symbol.

Let \$x\$ be the number of protons. The number of neutrons is \$\displaystyle x+0.317x=1.317x\$. The mass number is \$81\$. It is equal to the sum of the number of protons and the number of neutrons.\$\displaystyle 81 = x +1.317 x =2.317x \$\$\displaystyle x = 35 \$Hence, the symbol is \$\displaystyle _{35}^{81}Br \$.

Q: Sum of number of protons, electrons, and neutron in 12g of \${}_6^{12}C\$ is:

The atomic weight of carbon = 12 g and the given weight = 12 gAs we know that, \$\text{No. of moles} = \cfrac{\text{Given weight}}{\text{Molecular weight}}\$\$\therefore\$ No. of moles of Carbon in 12 g \$= \cfrac{12}{12} = 1 \text{ mole}\$No. of atoms present in 1 mole of Carbon \$= {N}_{A} = 6.023 \times {10}^{23}\$As 1 mole of carbon contains 6 electrons, 6 protons and 6 neutrons.\$\therefore \text{ No. of electrons in }6.023 \times {10}^{23} \text{ atoms of carbon} = 6 \times 6.023 \times {10}^{23}\$Similarly,\$\text{No. of protons in }6.023 \times {10}^{23} \text{ atoms of carbon} = 6 \times 6.023 \times {10}^{23}\$\$\text{No. of neutrons in }6.023 \times {10}^{23} \text{ atoms of carbon} = 6 \times 6.023 \times {10}^{23}\$\$\therefore\$ Sum of electrons, protons and neutrons in 12g of carbon = no. of electrons in 12 g carbon + no. of protons in 12 g carbon + no. of neutrons in 12 g carbon\$ = 6 \times 6.023 \times {10}^{23} + 6 \times 6.023 \times {10}^{23} + 6 \times 6.023 \times {10}^{23}\$\$= 108.414 \times {10}^{23} = 1.084 \times {10}^{25}\$So, the correct option is \$C\$

Q: Number of neutrons present in \$1.7\$ g of ammonia is:

Let us consider the problem.For, moles of \$N{H_3} = \frac{{1.7}}{{17}} = 0.1\$Let the Neutrons in 1 molecules of \$N{H_3} = 7 + 3 \times 0 = 7\$Hence,Number of Neurons \$= 0.1 \times {N_A} \times 7\$The correct answer is \$0.7{N_A}\$

Q: The order (lowest to highest) of e/m (charge/mass) ratio for electron (e), proton (p), neutron (n) and alpha particle \$(\alpha)\$ is:

The increasing order (lowest to highest) of e/m (charge/mass) ratio is \$ n < \alpha < p < e\$.Neutron being neutral has zero charges and lowest e/m ratio. An electron has a unit charge but negligible mass. Hence, the electron has a maximum e/m ratio.For an alpha particle, the e/m ratio is 2/4 or 0.5.For proton, e/m ratio is 1/1 or 1.

Q: The ion of an element has 3 positive charges. The mass number of the atom is 27 and the number of neutrons is 14. The number of electrons in the ion is:

From mass number and number of neutrons, we can calculate number of protons or electrons which is 13 (mass number - number of neutrons). Hence, the electronic configuration of this element would be 2, 8, 3. In order to become stable it would lose the last 3 electrons and gain 3 positive charges as given in the question. So, the resultant ion is left with 10 electrons. The element here is Al (aluminium).Hence correct option is (B).

Q: The mass of \$1\$ mole electron is \$0.55mg\$.

Mass of one electron is \$9.1 \times 10^{-28}gm\$So mass of one mole of electronis \$ ( 6.02 \times 10^{23} )\times ( 9.1 \times 10^{-28} )\$= \$0.55 \times 10^{-3}\$ gm \$=0.55mg\$ So, the given statement is true.

Chemistry

definition

Protons, Neutrons and Electrons

Proton- A sub-atomic particle with a positive charge and a unit mass.
Neutron- A sub-atomic particle with no charge and unit mass.
Electron- A sub-atomic particle with a negative charge and negligible mass.

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Subatomic Particles - Electron

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Reason Behind Discovery of Electron

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Subatomic Particles - Protons

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Discovery of Neutrons

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The mass of $1$ mole electron is $0.55 m g$ .

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definition

Protons, Neutrons and Electrons

REVISE WITH CONCEPTS

Subatomic Particles - Electron

Reason Behind Discovery of Electron

Subatomic Particles - Protons

Discovery of Neutrons

Quick Summary With Stories

Mass and Charge of Subatomic Particles

Which of the following statements is false?

If NA​ is Avogadro's number, then number of valence electrons in 4.2 g of nitride ion (N3−) is:

(i) Calculate the number of electrons which will together weighs one gram. (ii) Calculate the mass and charge of one mole of electrons.

An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.

Sum of number of protons, electrons, and neutron in 12g of 612​C is:

Number of neutrons present in 1.7 g of ammonia is:

The order (lowest to highest) of e/m (charge/mass) ratio for electron (e), proton (p), neutron (n) and alpha particle (α) is:

The ion of an element has 3 positive charges. The mass number of the atom is 27 and the number of neutrons is 14. The number of electrons in the ion is:

The mass of 1 mole electron is 0.55mg.

If $N_{A}$ is Avogadro's number, then number of valence electrons in 4.2 g of nitride ion $(N^{3 -})$ is:

(i) Calculate the number of electrons which will together weighs one gram.
(ii) Calculate the mass and charge of one mole of electrons.

An element with mass number $81$ contains $31.7 %$ more neutrons as compared to protons. Assign the atomic symbol.

Sum of number of protons, electrons, and neutron in 12g of $_{6}^{12} C$ is:

Number of neutrons present in $1.7$ g of ammonia is:

The order (lowest to highest) of e/m (charge/mass) ratio for electron (e), proton (p), neutron (n) and alpha particle $(α)$ is:

The mass of $1$ mole electron is $0.55 m g$ .