Chemical
Combination
Unit -1
Lesson -1
Made By
Dr. Niveen Fawzy
The atom & the ion
Element• Is composed of
Molecules
• Each
molecule
consists of
Atoms
The no. of well known elements are 116 elements
The atom is electrically neutral in ordinary state because no. of
positive protons are equal to the no. of negative electrons
Classification of elements
Elements are classified according to their
properties & electronic structure into:
1Metals
2-Non- 3-Noble
metals gases
First : Noble (inert) Gases
• They are elements in which the outermost electron
shells are completely filled with electrons , so they
don’t participate in any chemical combination in
ordinary conditions
• They are monoatomic
• They don’t form positive or negative ions in ordinary
conditions
Examples of noble gases
Atom of
inert gas
4
2𝐻𝑒
No. of
electrons
2
No. of
protons
2
No. of
neutrons
2
Electron
configuratio
n
K
2P
2n
2
20
10𝑁𝑒
10
10
10
L
K
10p
10n
2
40
18𝐴𝑟
18
18
22
K
18P
8
L M
Nobel gases
Second: Metals & non-metals
Physical properties of both
Chemical properties of both
Non-metals
Metals
They are elements which have
less than (4) electrons in the
outermost energy level
They are elements which have
more than (4) electrons in the
outermost energy level
During chemical reactions metals During chemical reactions nonlose (give) their outermost
metals gain electrons from other
electrons to other atoms &
atoms to complete the outermost
change to (+) ion
energy level & change to (-) ion
Mercury is the only liquid metal, while Bromine is the only liquid non-
Comparisons
Points of
comparison
Atom
Electrically:
Neutral
Ion
Charged (-) or
(+)
No. of electrons: Equal to the no. More or less
of protons
than no. of
protons
Examples of metals
Examples of metals
Examples of metals
Give reason:
• When the atom loses an electron or more during
chemical reaction, it changes into positive ion
• Because the no. of electrons becomes less than the no. of
protons
• What is an ion?
• Its an atom which loses or gains an electron or more
during chemical reactions
• What is a positive ion?
• Its an atom that loses one or more electrons during the
chemical reaction & carries a no. of positive charges
equal to the no. of given electrons
Examples of non-metals
Examples of non-metals
Examples of non-metals
Nitrogen atom
(N)
Nitrogen ion
(𝑁 −3)
Give reason:
• When the atom gains an electron or more during
chemical reactions , it changes into a negative ion
• Because the no. of electrons becomes more than the no.
of protons
• What is a negative ion?
• It’s the atom which gains an electron or more during the
chemical reaction & carries a no. of negative charges
equal to the no. of gained electrons
• N.B Hydrogen is a gaseous non-metal element although
it has only one electron in the outermost level (K)
Comparison
Positive ion (cation) Negative ion (anion)
A metal atom that loses an
electron or more during chemical
reaction
A non-metal atom that gains an
electron or more during chemical
reaction
It carries positive charges equal to It carries negative charges equal
the no. of lost electrons
to the no. of gained electrons
No. of electrons is less than no. of No. of electrons is more than no.
protons
of protons
No. of its energy levels is less
than that of its atom
No. of its energy levels is equal to
that of its atom
Try to think:
• What happens to the atomic diameter of an atom when
it loses or gains an electron or more?
• When an atom loses an electron or more its diameter &
volume decrease due to lackness of electrons, &
attraction of nucleus to remaining electrons increase , so
a positive ion diameter is smaller than its atomic
diameter
• When an atom gains an electron or more its diameter &
volume increase due to increase in the no. of electrons ,&
repelling increase between electrons , a negative ion
diameter is bigger than its atomic diameter
Chemical bonds
• Atoms combine together to form molecules
through chemical bonds
• We will study 2 types of bonds:
1- Ionic bond
2- Covalent bond
First: Ionic bond
• It’s a type of chemical bond that occurs between a metal
atom & a non-metal atom resulting from electric
attraction between a (+) &(-) ion
• Steps of formation of ionic bond:
1- Metal atom loses electron(s) & changes into a (+) ion
2- Non-metal atom gains electron(s) lost from metal atom
& changes into (-) ion
3- A strong electrical (electrostatic) attraction between (+)
& (-) ions occur through ionic bond
Examples of ionic bonds
1- Formation of
table salt
2-Formation of Magnesium oxide
First step
Second step:
:
Third step:
Second : Covalent bond
Its a bond occurred among atoms of non-metals through
the participation of each atom with the same no. of
electrons to complete the outer electron shell of each atom
Steps of formation of covalent bonds:
1- Two non-metal atoms interact together , no one loses or
gains any electrons
2- Each atom shares the other with a no. of electrons equal
to the no. needed to complete its outer shell
3- An interference occurred among both atoms resulting in
covalent bond
Types of covalent bond
• There are 3 types of covalent bonds:
• 1- Single covalent bond
• 2- Double covalent bond
• 3- Triple covalent bond
First: Single covalent bond
• Its bond arises between 2 non-metals sharing each other
with one electron
• Represented by one line joining the two atoms {
}
Examples of single covalent bond
•
1-Hydrogen molecule
Each hydrogen atom
shares with one
electron to complete
(K) level & become
more stable
Single covalent bond
•
2- Water molecule
The oxygen atom shares each
hydrogen atom with one electron ,
to complete the outermost shell of
all 3 atoms
Single covalent bond
• 3- Hydrogen chloride molecule:
• The hydrogen & chlorine atoms each share each other
with one electron
Double covalent bond
Oxygen molecule
The double covalent bond arises between 2 non-metal atoms sharing each other with 2
electrons & is represented by (=) joining 2 atoms
Each oxygen atom shares
the other with 2 electrons
to complete the outermost
shell (L) with 8 electrons &
become more stable
Triple covalent bond
Triple covalent bond arises between 2 non-metal atoms sharing each other with 3
electrons to complete the outermost shell & become more stable & is represented
by 3 lines
Nitrogen molecule
Comparison
Ionic bond
Covalent bond
Formed by losing or gaining of electrons
Formed by sharing one pair of electrons
or more
Arises between metal & non-metal
elements
Arises between 2 non-metal elements
Formed between 2 atoms of 2 different
elements
May be formed between 2 elements of
same element
Formed due to electrical attraction
between (+) &(-) ions
Formed due to sharing of electrons
between atoms
Its only one type
Three types : single , double , triple
Produces compound molecules only
Produces element & compound
Enrichment information
• The Egyptian scientist Ahmed Zweil has been granted
Nobel prize in chemistry in 1999 due to inventing new
brands of camera working via laser technologies
Model answers of book lesson 1-unit1
•
•
•
•
•
•
Question (1) (A):
1- Metal atom
2- Ionic bond
3-Non-metal atom
4- Triple covalent bond
5- Noble (inert) element
6- Metals
7- Non-metals
Question (1) (B):
Because iron is a metal element which is malleable so it
will not break, while coal is a non-metal which is not
malleable , breaks easily
Model answers of book lesson 1
Question (2) (A):
Atom
11𝑁𝑎
Electron
configuration
K L M N
2 8 1
-
17𝐶𝑙
2 8
7 -
7𝑁
2
- -
5
Molecule
NaCl
𝑁2
Type of bond
Ionic bond
Triple
covalent
Model answers of lesson 1
• Question (2) (B):
Model answers of lesson 1
• Question (3) (A):
Electron
configuration
K L M N
2 8 6 -
Its type
Its ion
Non-metal
𝑆 −2
12𝑀𝑔
2 8 2 -
metal
𝑀𝑔+2
18𝐴𝑟
2 8
inert gas
no ion
Element
16𝑆
8 -
Model answers of lesson 1
• Question (b) Give reason:
• 1- Because sodium (metal) atom joins with chlorine (nonmetal) atom by transferring one electron from Na to Cl &
ionic compound is formed . While chlorine atom joins
with other chlorine atom by sharing with one electron for
each atom to form covalent molecule.
• 2- Because the no. of electrons becomes less than no. of
protons
• 3- Because the no. of electrons becomes more than the
no. of protons
Model answers of lesson 1
• 4- Because ionic bond arises between 2 different atoms
(metal & non-metal) , while covalent bond arises
between 2 similar or different non-metal atoms
• 5- Because each oxygen atom shares with 2 electrons to
form double covalent bond
• 6- Because magnesium loses 2 electrons & change into
(+) ion , while oxygen gains the 2 electrons lost by (Mg) &
changes into (-) ion , then electric attraction occurs
between both ions
Model answers of lesson 1
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•
•
•
•
•
•
•
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Question (4): comparison:
Refer to previous slides for comparison tables
Question (5):
What is a positive ion?
Its an atom that loses one or more electrons during the chemical
reaction & carries a no. of positive charges equal to the no. of given
electrons
What is a negative ion?
It’s the atom which gains an electron or more during the chemical
reaction & carries a no. of negative charges equal to the no. of
gained electrons
What is an ion?
Its an atom which loses or gains an electron or more during
chemical reactions