Structure Of Atom - Class 11 Engineering Chemistry - Extra Questions

Value of $$l$$ = 0 to (n-1)
So, 1p and 3f are not possible.

Aufbau Principle states that in ground state of an ion, electrons fill atomic orbitals of lowest available energy levels before occupying higher levels.

(a) The average atomic mass of elements A and C $$\displaystyle = \dfrac{7+39}{2}$$ $$\displaystyle = \dfrac{46}{2}$$ $$\displaystyle =23$$

(b) The average atomic mass of elements A and C is the same as the atomic mass of element B=23.

(c) The element A is Lithium (Li), B is Sodium (Na) and C is Potassium (K). They are Dobereiner's Triads because in Dobereiner's Triads the atomic mass of the middle element is approximately the mean of the atomic masses of other two elements.

Given weight of water = 3.6 g

Molecular weight of water = 16 + 2 = 18 g

 

 

Given weight of carbon dioxide = 4.4 g

Molecular weight of carbon dioxide = 12 + 44 = 56 g

Aufbau principle says that electrons must be filled at first in the lower energy orbitals which can be known from n+l value. Value of this for 4s is less than that of the value of 3p. Hence that's the only reason why we fill 4s at first making calcium and potassium s-block elements. 

$$^{12}\textrm{C}$$ is the basis of atomic mass scale.
The atomic mass of $$^{12}\textrm{C}$$ is 12.000 atomic mass units abbrevated as 12.000 amu. 1 amu is 1/12th of the mass of an atom of carbon -12 equal to $$1.6605 \times 19^{-24} \: g$$

The element is oxygen having 8 protons, 8 electrons and 8 neutrons.
Recall that number of electrons in a shell is given by $$2n^2$$ where n denotes the number of the shell.

(i) The atom with atomic number 17 and mass number 35 is chlorine. Its complete symbol is $$\displaystyle _{17}^{35}Cl$$ .
(ii) The atom with atomic number 92 and mass number 233 is uranium. Its complete symbol is $$\displaystyle _{92}^{233}U$$ .
(iii) The atom with atomic number 4 and mass number 9 is beryllium. Its complete symbol is $$\displaystyle _{4}^{9}Be$$ .

For a given element, the number of protons is the same for the isotopes, whereas the mass number can be different for the given atomic number.
Hence, the mass number should be written necessarily.

Mass number is the sum of number of protons and neutrons which is indicated with letter $$A$$ .

False.
According to JJ Thomson's model of an atom:

(i) An atom consists of a positively charged sphere and the electrons are embedded in it.

(ii) The negative and positive charges are equal in magnitude. So, the atom as a whole is electrically neutral.

Mass number of Isotope $$1$$ = $$A$$

Atomic number is equal to Mass number- number of neutrons i.e. $$23-12=11$$ .

      $$\cfrac {1}{\lambda}=R \left[\cfrac {1}{n_1^{2}}-\cfrac {1}{n_2^{2}}\right]z^2$$                                 $$R= 1.097 \times 10^7; n_1=1; n_2=2$$

The Aufbau Principle states that in the ground state of an atom, an electron enters the orbital with lowest energy first and subsequent electrons are fed in the order of increasing energies.

$$\textbf{Given data:}$$

Given mass of Aluminium oxide ( $$Al_2O_3$$ ) = 0.051g

$$\textbf{Step 1: Calculate the molecular mass of Aluminium oxide.}$$

Molecular mass of $$Al_2O_3$$ = Mass of 2 Al atoms + Mass of 3 O atoms.

= (2 $$\times$$ 27) + (3 $$\times$$ 16) = 54 + 48 = 102 g/mol.

$$\textbf{Step 2: Calculate the number of moles of 0.051 g 0f aluminium oxide.}$$

$$No. of\ moles\ of\ Aluminium\ oxide$$ = $$\dfrac{Given\ mass\ of\ Aluminium\ oxide}{Molecular\ mass\ of\ Aluminium\ oxide}$$

$$No. of\ moles\ of\ Aluminium\ oxide$$ = $$\dfrac{0.051}{102}$$

$$No. of\ moles\ of\ Aluminium\ oxide$$ = $$0.0005 mol$$ .

$$\textbf{Step 3: Calculate the number of molecules of aluminium oxide in 0.051 g of aluminium oxide.}$$

1 mole of $$Al_2O_3$$ = $$6.022 \times 10^{23}$$ molecules of $$Al_2O_3$$

Therefore, 0.0005 mole of $$Al_2O_3$$ = $$6.022 \times 10^{23} \times 0.0005$$ molecules of $$Al_2O_3$$ = $$3.011 \times 10^{20}$$ molecules of $$Al_2O_3$$

$$\textbf{Step 4: Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.}$$

The number of aluminium ions ( $$Al^{3+}$$ ) present in one molecule of aluminium oxide is 2.

Therefore, the number of aluminium ions ( $$Al^{3+}$$ ) present in $$3.011 \times 10^{20}$$ (0.051 g) molecules of $$Al_2O_3$$ = $$2 \times 3.011 \times 10^{20}$$ = $$6.022 \times 10^{20}$$

$$\textbf{Conclusion:}$$

Therefore, the number of aluminium ions present in 0.051 g of aluminium oxide is  $$6.022 \times 10^{20}$$

According to the given table the number of protons present in A,B,C,D and E are 1,3,7,18, and 20 and neutrons are 0,4,7,22,20 respectively.

Mass number is the sum of the number of protons and neutrons present in the nucleus of an atom. It is denoted by A.

Electron

Mass number

Aufbau principle is also known as the building up principle. According to this principle, "Electrons should enter the subshells in the order of increasing energies".

The Aufbau principle dictates the manner in which electrons are filled in the atomic orbitals of an atom in the ground state. It states that electrons are filled in atomic orbitals in the increasing order of orbital energy level. According to the Aufbau principle, the available atomic orbitals with the lowest energy levels are occupied before those with higher energy levels.

Salient features of the Aufbau Principle are :

• According to Aufbau's principle, electrons first occupy those orbitals whose energy is the lowest. This implies that the electrons enter the orbitals having higher energies only when orbitals with lower energies have been completely filled.
  

• The order in which the energy of orbitals increases can be determined with the help of the $$(n+l)$$ rule, where the sum of the principal $$(n)$$ and azimuthal $$(l)$$ quantum numbers determines the energy level of the orbital.

• Lower $$(n+l)$$ values correspond to lower orbital energies. If two orbitals share equal $$(n+l)$$ values, the orbital with the lower $$n$$ value is said to have lower energy associated with it.

• The order in which the orbitals are filled with electrons is : $$1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p,$$ and so on.

The Aufbau principle dictates the manner in which electrons are filled in the atomic orbitals of an atom in its ground state. It states that the electrons are filled in the atomic orbitals $$(s,p,d,f)$$ in an increasing order of orbital energy level. 

Mass of magnesium in 3.00 g of chlorophyll 
$$= \frac {2.68 \times 3}{100}= 0.080 g$$
24.3 g of Mg contain $$= 6.02 \times 10^{23}$$ atoms 
0.080 g of Mg contain   $$=\frac{6.02 \times 10^{23}}{24.3} \times 0.080$$
$$= 1.98 \times 10^{21}$$ atoms

An atomic spectrum is a spectrum that has been shined through or originates from a material (usually a gas) and contains patterns that are characteristic of the elements present in the material.