CHEMICAL BONDING
Chemical bonding deals with the various types of forces of attraction that binds atoms and molecules together. There are two major types: -
Electrovalent bonding/Ionic bonding
2.Covalent bond bonding.
I. Ordinary covalent
II. Dative covalent
Electrovalent bonding or IONIC BOND: - This is a type of bonding that involves the total transfer of electrons from one atom (usually a metal) to another atom (usually a non-metal).
It is also called ionic bonding because the compound splits into ions when dissolved in water or when molten
This type of bond is usually identified by looking at the two atoms involved in the bonding. It is usually between a metal and a non-metal.
Examples include the bonding between sodium and chlorine.
Using Lewis electron dot symbol: Lewis dot electron symbol uses the symbol of the element surrounded by the valence electrons of the
Characteristics of Electrovalent bonds
1. They have high melting and high boiling points.
II. They are soluble in polar solvents (e.g water)
III. They conduct electricity when molten or in solution
IV. They are crystalline in nature
V. They are solids at room temperature.
Covalent bonding
Covalent bonding can be of two types
i. ordinary covalent bonding and
ii. dative or coordinate covalent bonding.
Ordinary COVALENT BONDING: - This is a type of bonding that involves the sharing of electrons between two atoms (usually non-metals).
Ordinary covalent bonds can be identified by looking at the two atoms involved in the bonding. If the two atoms involved in the bonding are both non-metals then the bond is possibly covalent bond.
Ordinary covalent bonding can be grouped into three types
i. Single covalent bond: - In this type of covalent bond each atom donates one electron each to the shared pair. Examples include the bonding between two hydrogen atoms to form a hydrogen molecule or two chlorine atoms to form a chlorine molecule
i.
ii.
Here you can see only one dash (representing the b0ond between the hydrogen atoms and the chlorine atoms).
ii. Double Covalent Bond: - In this type of covalent bonding each atom donates two electrons to the shared electron pair. Examples include the bonding between two Oxygen atoms to form an Oxygen molecule, and also the bonding between carbon and oxygen to form Carbon (IV) oxide
i.
O + O → O=O ( O2)
Covalent bonding does not exist only between atoms of the same element, it can occur between atoms of different elements. For example, the combination of carbon and oxygen to form carbon (IV) oxide
using Lewis dot electron symbol
C + 2O → O==C==O
Here there are two lines/dash (representing double covalent bonds) between the the two atoms
iii. Triple Covalent bond: - In this type of bonding, each atom donates three electrons each to the shared electron pair. An example includes the bonding between nitrogen atoms to form the molecule (N2)
1. N + N → N2
Note: In all these examples of covalent combinations, each atom is contributing the same number of electrons it needs to acquire an octet or a duplet (in the case of hydrogen) structure.
Characteristics of Covalent bond
I. Solids have low melting and low boiling points.
2. They are insoluble in polar solvents but soluble in organic solvents.
3. They are mainly volatile liquid or gases at room temperature.
4. They form molecules not ions.
5. They are non-electrolytes.
DATIVE COVALENT BOND: - This is a type of covalent bond that involves the sharing of electrons between two atoms, but unlike ordinary covalent bonding the shared electron pair is donated by only one of the two atoms.
Example of dative covalent bond is the bond in ammonium ion NH4+ and hydroxonium ion H3O+.
So, the basic difference between ordinary covalent and dative covalent bond is that the shared electron pair is donated by only one of the two atoms involved in the bonding.
METALLIC BONDING: - This is the attraction between the positive nuclei of metals and the electron cloud or sea of electrons enveloping the nucleus
.
Positively charged electrons embedded in a sea of delocalized electrons
HYDROGEN BONDING: - Hydrogen bonding is a type of force (bond) that arises when hydrogen is bonded covalently to a strongly electronegative element.
Hydrogen bond can only exist in compounds where hydrogen is bonded to another nonmetal which is highly electronegative. Example of electronegative elements include Fluorine, Oxygen, Chlorine, Nitrogen.
Electronegativity is the tendency of an element to attract electrons to itself in a molecule
H-F.......H-F,,,,,,H-F the dotted lines represent hydrogen bonding. hydrogen bonding gives added properties to compounds they occur in such as higher boiling points; and such covalent compounds usually exist in the liquid state. example is water.
Van der Waals Forces:
These are Weak intermolecular forces of attraction arising from temporary dipoles in molecules.
Van der Waals forces are weaker than covalent bonds.
They arise sometimes from temporary uneven distribution of electrons. ( temporary dipoles)
Examples of substances where van der waals are found include Iodine crystals, between graphite layers.
OBJECTIVE QUESTIONS
1. What is responsible for metallic bonding?
(a). Shearing of electrons between the metal atoms.
(b). Attraction between the atomic nuclei and cloud of electrons.
(c). Transfer of electrons from one atom to another
(d). Attraction between negative and positive ions.
2. Electrostatic forces of attraction between sodium ion and halide are greatest in
(a) NaCl.
(b) NaBr.
(c) NaF .
(d) NaI
3. Which of the following compounds is covalent?
(a). CaCl2
(b). MgO
(c). NaH
(d). CH4.
4. The type of chemical bond that exist between potassium and oxygen in potassium oxide is
(a) Ionic
(b) metallic
(c) covalent
(d) dative
5. Which type of bond is represented by the dotted lines in the following structure?
H-F''''''''H-F''''''''H-F'''''''H-F
(a) Covalent bond
(b) Dative bond
(c) Electrovalent bond
(d) Hydrogen bond.
6. What type of bond will be formed between elements P and Q if their electronegativity values are 0.8 and 4.0 respectively
(a) Covalent bonding
(b) Co-ordinate covalent bonding
(c) Electrovalent bonding
(d)Hydrogen bonding
7. A solid substance with high melting and boiling points is likely to be a/an
(a) covalent compound
(b) dative covalent compound
(c) electrovalent compound
(d) non-metal
8. Which of the following molecules has a triple bond
(a) CH4
(b) NH3
(c) N2
(d) O2
9. Which of the following molecules has a linear shape?
(a) CH4
(b) CO2
(c) H2S
(d) NH3.
10. Hydrogen bonds are formed between molecules containing a hydrogen atom bonded to a
(a) strongly electronegative atom
(b) non-polar species
(c) diatomic element
(d) complex ion.
11. Element X with electronic configuration 2,8,2 and an element Y with electronic configuration 2,8,7 are likely to combine by
(a) metallic bonding
(b) covalent bonding
(c) electrovalent bonding
(d) dative bonding
12. Which of the following statements is correct about sodium chloride in the solid state?
(a) It exists as aggregates of ions
(b) it conducts electricity
(c) its melting point is below 1000C
(d) it exists as discrete molecules.
13. If an element with high electron affinity combines with another element with low ionization energy, the bond formed will be mainly
(a) covalent
(b) ionic
(c) dative
(d) metallic
14. The bond formed when two electrons that are shared between two atoms are donated by only one of the atoms is
(a) covalent dative
(b) dative
(c) ionic
(c) metallic.
15. When element 20A combines with element 8Y.
(a) a covalent compound AY is formed
(b) an ionic compound AY is formed
(c) an ionic compound A2Y is formed
(d) a covalent compound AY2 is formed.
16. In metallic solids the forces of attractions are between the mobile valence electrons and
(a) Atoms
(b) Neutrons
(c) The negative electrons
(d) positively charged nuclei.
17. which of the following compounds has hydrogen bonds between its molecules
(a). HF
(b). HBr
(c). HCl
(d). HI
18. The bonds in crystalline ammonium chloride are
(a) covalent and dative
(b) ionic and covalent
(c) ionic, covalent and dative
(d) ionic, covalent and hydrogen bond.
19. Which of the following properties of covalent compounds is not correct? They
(a) are non-electrolytes
(b) are mostly gaseous and volatile liquids.
(c) Have low melting points
(d) have high boiling points.
20. Which of the following molecules is not linear in shape?
(a) CO2
(b) O2
(c) NH3
(d)HCl.
21. In bonded atoms, increase in electronegativity difference,
(a) increases polarity
(b) decreases polarity
(c) has no effect on polarity
(d) brings the polarity to zero.
22. If the difference between the electronegativities of two element is large, the type of bond that can be formed between them is
(a) covalent
(b) dative
(c) ionic
(d) metallic.
23. Which of the following species does not contain a co-ordinate bond?
(a) Al2Cl3
(b) CCl4
(c) H3O+
(d) NH4+
24. Which of the following compounds has hydrogen bonds between its molecules?
(a) HF
(b) HBr
(c) HCl
(d) HI
25. What type of chemical bonding is involved in the formation of NH4+ from a molecule of ammonia and a proton?
(a). Covalent bonding
(b). Co-ordinate covalent bonding
(c). Electrovalent bonding
(d). Hydrogen bonding
26.
THEORY QUESTIONS
1a) Define i. electrovalent bond
ii. Give two properties of electrovalent bond
iii. With the aid of a diagram show the bonding between sodium and chlorine to form sodium chloride.
(b)i Define covalent bond
ii. Give three properties of covalent bond
iii. With the aid of a diagram show how ammonia molecule is formed
(c). State the type of bonds that exist in
i. ammonia
ii. ammonium ion.
2a) Define the following terms
i. electrovalent bonding
ii. ordinary covalent bonding
iii. give two properties of electrovalent bond
iv. with the aid of a diagram show the bonding between magnesium and chlorine to form magnesium chloride.
bi) differentiate between ordinary covalent and dative covalent bond
ii. Define hydrogen bonding
3.a(i) Why do electrovalent compounds have high boiling points
(ii). Name two compounds that can react with hydrogen ion to form dative bond
2 comments:
Wow thanks a lot ma it much easier this way to read and understand
Thanks a lot ma I have learned a lot
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