Question

How many inner, outer, and valence electrons are present in an atom of each of the following elements?

Answer 1

Answer:

For a: The number of inner electrons, outer electrons and valence electrons are 28, 7 and 7 respectively.

For b: The number of inner electrons, outer electrons and valence electrons are 54, 1 and 1 respectively.

For c: The number of inner electrons, outer electrons and valence electrons are 23, 1 and 1 respectively.

For d: The number of inner electrons, outer electrons and valence electrons are 36, 2 and 2 respectively.

For e: The number of inner electrons, outer electrons and valence electrons are 2, 7 and 7 respectively.

Explanation:

Outer shell electrons are the electrons which are not tightly held by the electrons. They are called as valence electrons. The electrons present in the highest principle quantum number are known as valence electrons.

Inner shell electrons are the electrons which are tightly held by the electrons. They are called as core electrons.

Inner electrons = Total number of electrons - Valence electrons

Total number of electrons in an atom is equal to the atomic number of the element.

For the given options:

• Option a:  Bromine (Br)

Bromine is the 35th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^23d^{10}4p^5$

Highest principle quantum number is 4

Number of valence electrons = 7

Number of outer electrons = 7

Number of inner electrons = 35 - 7 = 28

• Option b:  Cesium (Cs)

Cesium is the 55th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^23d^{10}4p^65s^24d^{10}5p^66s^1$

Highest principle quantum number is 6

Number of valence electrons = 1

Number of outer electrons = 1

Number of inner electrons = 55 - 1 = 54

• Option c:  Chromium (Cr)

Chromium is the 24th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^13d^{5}$

Highest principle quantum number is 4

Number of valence electrons = 1

Number of outer electrons = 1

Number of inner electrons = 24 - 1 = 23

• Option d:  Strontium (Sr)

Strontium is the 38th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^23d^{10}4p^65s^2$

Highest principle quantum number is 5

Number of valence electrons = 2

Number of outer electrons = 2

Number of inner electrons = 38 - 2 = 36

• Option e:  Fluorine (F)

Fluorine is the 9th element of the periodic table having electronic configuration of $1s^22s^22p^5$

Highest principle quantum number is 2

Number of valence electrons = 7

Number of outer electrons = 7

Number of inner electrons = 9 - 7 = 2