Electronic arrangement of atoms

1
Electronic arrangement of atoms(??????)
2
Development of atomic models
3
Bohrs Model

• According to Bohrs Model of atom, electrons are
  orbiting (?????) around the nucleus in different
  shells. And different shells hold different no.
  of electrons.

4
Electronic configuration (????) of atoms

• According to some other experiments (Will be
  studied in Alevel), atoms are found to have
  different no. of electrons in individual orbits
  (??).
• The electrons in an orbit is said to form an
  electron shell (???).
• The arrangement (??) of electrons in an atom is
  known aselectronic configuration (????).

5
Electronic configuration (????) of atoms

• A sodium atom has 11 electrons and are arranged
  in 3 shells.
• The electronic configuration can be represented
  as follows

By electron diagram
By notation
An electron may be represented by a cross (), a
dot () or the symbol (e-)
2, 8, 1
1st shell
2nd shell
3rd shell
6
Electronic configuration (????) of atoms of the
first 20 elements
For the first 20 elements, it is found that the
maximum no. of electrons that each shell can hold
is limited. Shell Maximum no. 1 2 2 8
3 8 (18 for other elements)
7
? State the electronic configurations of

• Nitrogen
• Calcium
• Chlorine

8
? State the electronic configurations of

• Nitrogen
• Calcium
• Chlorine

2, 5
9
? State the electronic configurations of

• Nitrogen
• Calcium
• Chlorine

2, 5
2, 8, 8, 2
10
? State the electronic configurations of

• Nitrogen
• Calcium
• Chlorine

2, 5
2, 8, 8, 2
2, 8, 7
11
Drawing of electron diagram

• In the drawing, the electrons should fill up the
  shells in a particular order. Except the first
  shell, the electrons fill up the four corners
  of the shell before pairing up.

12
? Draw the electron diagrams of

• Nitrogen
• Calcium
• Chlorine

13
? Draw the electron diagrams of

• Nitrogen
• Calcium
• Chlorine

14
? Draw the electron diagrams of

• Nitrogen
• Calcium
• Chlorine

15
? Draw the electron diagrams of

• Nitrogen
• Calcium
• Chlorine

16
Electronic configuration (????) of atoms of the
first 20 elements
17
Electronic configuration (????) of atoms of the
first 20 elements
For the first 20 elements, it is found that the
maximum no. of electrons that each shell can hold
is limited. Shell Maximum no. 1 2 2 8
3 8 (18 for other elements)
18
Stability (???) of noble gas (??) configuration
19
Stability (???) of noble gas (??) configuration
20
Octet rule (?????)

• Besides helium, all noble gases have 8 outermost
  shell electrons. An electron shell with 8
  electrons is known as an octet (???). An atom
  with an octet is said to be exceptionally (???)
  stable.
• Helium has only 2 electrons in the outermost
  shell. It is said to have a duplet.
• In general, an atom with a completely filled
  outermost shell (valence shell) would be more
  stable.