Name: Electron Distribution of First 20 Elements
Uploaded: 2019-07-19
Duration: 3 min 58 s
Description: On increasing the atomic number in the first 20 elements, the electronic structure builds up one electron. Let’s explore the electron distribution of the fir...

Question

Write the rules proposed for electron distribution under the Bohr-Bury scheme. Use the rules to write the electronic configuration of given atoms. Also, give the number of neutrons present in each atom.

${}_{9}^{19}F, {}_{12}^{24}{Mg}, {}_{14}^{28}{Si}, {}_{15}^{31}P, {}_{17}^{35}{Cl}$

Accepted Answer

The rules proposed for electron distribution under the Bohr-Bury scheme are:

The maximum number of electrons present in a shell is given by the formula $2 n^{2}$ , where ' $n$ ' is the shell number. For $K$ shell (orbit), $n = 1$ and for $L, M, N$ shells, $n = 2, 3, 4$ respectively. The maximum number of electrons in first orbit or $K$ -shell will be $2 \times 1^{2} = 2$ and similarly, we can calculate the maximum number of electrons in other shells. The electrons present in the outermost shell are called valence electrons and this shell is called the valence shell.

The maximum number of electrons that can be accommodated in the outermost shell is $8$ . (Exception is when $K$ is the outermost shell and the maximum number of electrons is then $2$ )

Electrons are not accommodated in a given shell, unless the inner shells are filled. That is, the shells are filled in a step-wise manner.

Even when the capacity of the penultimate shell is more than $8$ , a ninth electron is placed in it only after $2$ electrons have entered the last shell. For example, the atomic number of calcium is $20$ but its electronic configuration is $2, 8, 8, 2$ and not $2, 8, 9, 1$ .

The electronic configuration is the distribution of electrons in different shells of an atom. Therefore, the electronic configuration of the given atoms are:

Atom Atomic number (Number of electrons) Electronic configuration

${}_{9}^{19}F$ $9$ $2, 7$

${}_{12}^{24}{Mg}$ $12$ $2, 8, 2$

${}_{14}^{28}{Si}$ $14$ $2, 8, 4$

${}_{15}^{31}P$ $15$ $2, 8, 5$

${}_{17}^{35}{Cl}$ $17$ $2, 8, 7$

The atomic number is the number of protons in the nucleus of an atom. The number of neutrons can be calculated from the mass number of the given atoms. That is,

Number of neutrons $=$ Mass number $-$ Number of protons. Therefore, the number of neutrons of the given atoms can be given as,

Atom Atomic number (Number of protons) Mass number Number of neutrons (Mass number $-$ Number of protons)

${}_{9}^{19}F$ $9$ $19$ $19 - 9 = 10$

${}_{12}^{24}{Mg}$ $12$ $24$ $24 - 12 = 12$

${}_{14}^{28}{Si}$ $14$ $28$ $28 - 14 = 14$

${}_{15}^{31}P$ $15$ $31$ $31 - 15 = 16$

${}_{17}^{35}{Cl}$ $17$ $35$ $35 - 17 = 18$

Element	Symbol	No. of electrons	Distribution of electrons in different orbits				Electronic configuration	Valence electron
Element	Symbol	No. of electrons	$K$	$L$	$M$	$N$	Electronic configuration	Valence electron
Hydrogen	$H$	$1$	$1$				$1$	$1$
Lithium	$Li$	$3$	$2$	$1$			$2, 1$	$1$
Carbon	$C$	$6$	$2$	?			?	?
Oxygen	$O$	$8$	?	?			?	?
Sodium	$Na$	$11$	$2$	?	$1$		$2, 8, 1$	?
Aluminium	$Al$	$13$	$2$	$8$	?		?	?
Phosphorous	$P$	$15$	$2$	$8$	?		?	?
Chlorine	$Cl$	$17$	?	?	?		?	?
Argon	$Ar$	$18$	$2$	$8$	$8$		?	?
Potassium	$K$	$19$	$2$	$8$	$8$	?	?	$1$
Calcium	$Ca$	$20$	?	?	?	$2$	?	?

Element	Symbol	Number of protons	Mass number	No. of neutrons
Hydrogen	$H$	$1$	$1$
Lithium	$Li$	$3$	$6$
Carbon	$C$	$6$	$12$
Oxygen	$O$	$8$	$16$
Sodium	$Na$	$11$	$23$
Aluminium	$Al$	$13$	$27$
Phosphorous	$P$	$15$	$31$
Chlorine	$Cl$	$17$	$35$
Argon	$Ar$	$18$	$40$
Potassium	$K$	$19$	$39$
Calcium	$Ca$	$20$	$40$

Write the rules proposed for electron distribution under the Bohr-Bury scheme. Use the rules to write the electronic configuration of given atoms. Also, give the number of neutrons present in each atom.

${}_{9}^{19}F, {}_{12}^{24}{Mg}, {}_{14}^{28}{Si}, {}_{15}^{31}P, {}_{17}^{35}{Cl}$

Important Questions on Atomic Structure

Learn and Prepare for any exam you want !

Write the rules proposed for electron distribution under the Bohr-Bury scheme. Use the rules to write the electronic configuration of given atoms. Also, give the number of neutrons present in each atom. F919, Mg1224, Si1428, P1531, Cl1735

Important Questions on Atomic Structure

Learn and Prepare for any exam you want !

Write the rules proposed for electron distribution under the Bohr-Bury scheme. Use the rules to write the electronic configuration of given atoms. Also, give the number of neutrons present in each atom.

${}_{9}^{19}F, {}_{12}^{24}{Mg}, {}_{14}^{28}{Si}, {}_{15}^{31}P, {}_{17}^{35}{Cl}$