Biology and Chemistry grade 10 notes

↳
Atoms

atomic no




&
PROTONS :
3 Atomic numbe
-




L I ELECTRONS
alomic protons
mass) 6 94 .




NEUTRONS :

Atomic mase -




Atomic numbe




~

* I
Molecules
·
A molecule is a group of two or more atoms that are the same element held together by chemical bonds.
Compounds or molecular compounds are two or more atoms of different elements held together by chemical
bonds.




&D

, immud
Lewis dot diagram

Bonding capacity: Electrons the last valence needs to be complete-> 1st: 2 2nd: 8 3rd: 8 4th: 18
If bonding capacity is 0, then the element is non-reactive.
Valence electrons: Number of electrons on the last valence.




How to draw a Lewis Dot Diagram: >
-




1) Count all the valence electrons used for atoms
Bonds are

to share v.e so that they
are complete
.




-
2) Draw the central atom. (The one there is only one of)
O
L

3) Draw other atoms and connect them with single bonds.
valence electrons : 8-4 : 4 ve left
H -

O -
H
4) Put remaining valence electrons so that the centre atom has 8 (full valence). If we have
more left and centre one already has eight then the others have to have 8 too.
v e
.
left = 4 -
4 =
@




has to
↑




1The no bonds it has
of
be the same as the bonding
capacity of each element !