Chemical Reactivity The reactivity of an element depends on the number of valence electrons If the outer shell of an atom already contains 8 valence electrons this means the atom has ID: 701071
Download Presentation The PPT/PDF document "Bonding Introduction for Science 10" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Bonding
Introduction for Science 10Slide2
Chemical Reactivity
The reactivity of an element depends on the number of
valence electrons
.
If
the outer shell
of an atom already
contains
8 valence electrons
, this means
the atom has
a
stable octet
and is
unreactive
(e.g. noble gases).
If the outer shell has
less than 8
valence electrons, the atom is unstable and
reactive
(e.g. fluorine).
In this case,
electrons are transferred from
one
atom to another
or shared between them so
that the atoms can have the stable electron arrangements of the noble gases (8 valence electrons). Slide3
Ion Formation
Atoms that lose or gain electrons to become stable are called
ions
.
The
ionic charge
is the charge the element will take on if it loses or gains
electrons.
1)
Cations
are m
etals
that lose electrons
and
form positive ions (Na
+
).
Some metals
are
polyvalent
, meaning they can
have more than one charge
(
Fe
2+
or Fe
3
+
).
2)
Anions
are non-metals which gain electrons and form negative ions (O
-2
).Slide4
Cations v
s AnionsCations
Element
Total
e
-
Valence
e
-
To bond…IonSodium111Lose 1 e-Na+1Magnesium122Loses 2 e-Mg+2Aluminum133Loses 3 e-Al+3Calcium
Anions
Element
Total
e
-
Valence
e
-
To
bond…
Ion
Chlorine
17
7
Gain 1
e
-
Cl
-1
Oxygen
8
6
Gains 2
e
-
O
-2
Nitrogen
7
5
Gains 3
e
-
N
-3
SulfurSlide5
Forming Compounds
When atoms combine by transferring or sharing their electrons, they are said to have
bonded
and formed a
compound
.
Compounds can be formed by either ionic bonding or covalent bonding.Slide6
Ionic Bonds
Formed
between
metals
and
non-metals
.
Valence
electrons are
transferred from metal cation to non-metal anion. Compounds formed using ionic bonds are referred to as ionic compounds. (Eg. Li2O)
Lithium
Oxygen
+
Electrons are transferred from the cations to the anion
Li
+
O
2-
Li
+
Lithium oxide,
Li
2
OSlide7
Covalent Bonds
Formed
between two or more
non-metals
Valence
electrons are
shared
between atoms
Compounds formed using covalent bonds are referred to as molecules. (Eg. HF)
Hydrogen
Fluorine
+
Electrons are shared
Hydrogen fluorideSlide8
Diatomic Molecules
A special type of molecule is called a
diatomic
molecule. It occurs when 2 atoms of the
same element
share their valence electrons.Slide9
Diatomic MoleculesSlide10
Diatomic MoleculesSlide11
Ionic vs Covalent Properties
Ionic
Covalent
Examples
Sodium Chloride (
NaCl
- salt)
Carbon Dioxide
(CO
2)Physical StateSolid at room temp Liquids & gases at room tempMelting & Boiling PointsHighLowSolubility in WaterHigh (meaning soluble)Low (insoluble)Electrical ConductivityHigh (meaning conducts electricity)Low (does not normally conduct electricity)Slide12
Any questions?