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NIS – PHYSICAL SCIENCE
Lecture 85 – Lecture 86 – Lecture 87
Types of Bonds
Ozgur Unal
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Types of Bonds
What is wrong with this person?
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Types of Bonds
In a compound, atoms are held together
by attractive electric forces.
A chemical bond is the force that holds
atoms together in a compound.
A compound has different chemical and physical properties
from those of the atoms that make up the compound.
Remember that atoms in a compound
can lose, gain or share electrons.
There are two types of compounds:
Ionic compounds  Gain-lose electrons
Covalent compounds  Share electrons
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The Ionic Bond
Consider the elements K and I.
What are their group numbers?
How many electrons are there in their outer energy levels?
K and I for the compound KI.
K loses one electron  K+
I gains one electron  IWhat is the total charge of the compound KI?
An ionic bond is the force of attraction between the opposite
charges of the ions in an ionic compound.
The result of this bond is a neutral compound.
Metals and non-metals usually combine by forming ionic
bonds.
http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/bom1s2_11.swf
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Sharing Electrons
How do Group 14 elements,
such as C and Si, form
compounds?
Some elements share electrons to
become more chemically stable.
By sharing electrons, atoms can have
8 electrons in their outer energy level.
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Sharing Electrons
The attraction that forms between atoms when they share
electrons is known as a covalent bond.
Covalent bond forms between nonmetallic elements!
A neutral particle that forms as a result of electron sharing is
called a molecule.
Example: CH4, H2, H2O etc.
Single Covalent Bond:
A single covalent bond is made up of two
shared electrons.
Example: A H2O molecule has 2 single
covalent bonds.
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Sharing Electrons
Multiple Covalent Bonds:
A covalent bond also can contain more than one pair of
shared electrons  multiple (double or triple) covalent bond
Example: N2  triple covalent bond
CO2  double covalent bond
Any other examples?
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Sharing Electrons
If you were to share food with a
heavy weight lifter, would you eat
equal amounts of food?
As pair(s) of electrons are shared in a covalent compound,
the sharing might not be equal.
The strength of attraction of each atom to its electrons is
related to:
the size of the atom
the charge of the nucleus
the total number of electrons the atom contains
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Sharing Electrons
Example: HCl
The shared electrons feel a stronger
attraction to Cl, rather than H.
These shared electrons will spend more time near the Cl
atom than near the H atom.
As a result of this, the Cl end of the molecule will have a
negative partial charge shown by δ-.
The H end of the molecule will have a positive partial charge
shown by δ+.
Check out Figure 14!!
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Sharing Electrons
Not all molecules have unequal sharing of electrons.
Example: H2, O2, N2 etc. share the electrons equally.
In order to distinguish these molecules we use the terms
polar and nonpolar.
A polar molecule is one that has a slightly positive end and a
slightly negative end  Overall molecule is neutral!!
Example: H2O, HF etc.
A nonpolar molecule is one in which electrons are shared
equally in bonds.
Example: H2, CCl4 etc.
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Properties of Compounds
Recall that atoms can form two types of bonds: covalent and
ionic.
Example: Sugar  covalent bond
Salt  ionic bond
How do you compare the physical and chemical properties of
sugar and salt?
The chemical and physical properties of covalent compounds
and ionic compounds are different  Table 2!!
Why?
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