tutorial_i-2_atomic_structure_and_bonding.pdf

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TUTORIAL CHAPTER I-2: ATOMIC STURCTURE AND BONDING

EXAMPLES

EXAMPLE 2.3Make up the double bond between 2 oxygen atoms for O2. Atomic number for O is 8.

ANSWER

Steps to draw orbital model:

i. Write down the electron configuration for the atom based on the atoms

atomic number,

(O, Z = 8) = 1s2 2s22p4

ii. Draw the orbital model based on the orbital number for the atom,

EXAMPLE 2.2

Between Natrium and Chlorine, which one will become electropositive ion and which one

will become electronegative ion in a chemical reaction?

Given that the electronegativity value for Na = 0.9 and that of Cl = 3.0

ANSWER:

Natrium is tend to give up its electron because of the lower electronegativity value

compared to chlorine. Chlorine will have more tendency of attracting electrons towards its

atom in a chemical reaction with Natrium.

So, Natrium will be electropositive ion and chlorine will be electronegative ion.

EXAMPLE 2.1

For sodium with Z = 11, write down its electron configuration.

ANSWERThe way to write the electron configuration:

Therefore, by referring to Figure 2.11; the electron configuration for sodium (Na) will be:

1s22s

22p

63s

1

1 s2

Principalquantumnumber

Orbitalquantumnumber

No. of electron inthe orbital


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O, n= 2

iii. Figure out the number of valence electron/s to know how many electrons

will take part in the chemical reaction.O = 6

iv. Figure out the number of electron sharing needed 2 pairs of electron

sharing is needed to fill up the outermost orbit

v. Check the electronegativity value to figure out whether it is a polar or non-

polar covalent bonding. For this case since both are the same elements, it is

a non-polar covalent bonding.

vi. Draw the orbital model to show the sharing that takes place.

TRY IT YOURSELF!

1. Try to work out the ionic bonding process between magnesium (Z=12) and

oxygen (Z=8). The electronegativity value for Mg is 1.2 and that of O is 3.5.

See if you can explain it step by step using the orbital model

2. Can you figure out how water molecules bound to each other? Describe

their intermolecular bonding

TUTORIAL

1. Write the electron configuration of the following atoms and its ions by using the

spdf notation. Natrium (Z= 11), Magnesium (Z=12), Aluminium (Z=13), carbon

(Z=6), Nitrogen (Z=7), Oxygen (Z=8), Neon (Z=10), Chlorine (Z=17) and Argon

(Z=20). Are there any atoms that you cannot figure out its ions configuration?

Why and what are these elements called?


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2. For those elements in Q1 that can become ions, determine its valence

electron. What is the importance of these valence electrons in chemical

reaction?

3. What is electronegativity? Why is it important in chemical reaction?

4. Based on its electronegativity value, will Magnesium be electropositive or

electronegative ions during a chemical reaction with Oxygen? Why? (Mg=1.2,

O=3.5)

5. What is the difference between ionic bonding and covalent bonding? Which

one would normally occurs between non-metal and non-metal elements? Can

you give an example to it?

6. What is the difference in the bonding between carbon atoms in CO2 and CH4 ?

7. Describe the bonding that occurs between H and Cl in Hydrochloric acid (HCl).

How does each HCl molecules bonded to each other?

8. Magnesium and oxygen combined with each other through the ionic bonding.

After ionization process takes place, which ion will become larger and which

ion will become smaller than its neutral state? Why?

9. Try to work out the ionic bonding process between magnesium (Z=12) and

chlorine (Z=17). The electronegativity value for Mg is 1.2 and that of Cl is 3.0.

See if you can explain it step by step using the orbital model

10. Magnesium oxide (MgO) and sodium chloride (NaCl) are both ionic

compounds. The melting point of MgO is 2800oC while that of NaCl is 800oC.

Can you figure out why the melting point of MgO is much higher than that of

NaCl? Hin t: it has something to do with their valence electrons.

11. Now that we have gone through all three primary types of bonding, can you

explain why pure aluminium (Al) is ductile while aluminium oxide (Al2O3) is

brittle in nature?

12. Can you figure out how water molecules bound to each other? This is what

makes water a very good solvent. Try to work out how your table salt (NaCl)

dissolves in water using all the bonding knowledge that you have learnt so far

13. Methane has a much lower boiling temperature than does water. Explain why

this is true in terms of the bonding between molecules in each of these two

substances

14. Both graphite and diamond are made of carbon atoms. Why do they have such

a huge different in their properties i.e. one is soft and flaky but the other one isone of the hardest substance in the world?


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SOLUTION (TRY IT YOURSELF!)

Q1. Steps to draw orbital model:

Write down the electron configuration for the atom based on the atoms atomic

number,

(Mg, Z=12) = 1s2 2s22p63s2

(O, Z = 8) = 1s2 2s22p4

Draw the orbital model based on the orbital number for the atom,

Mg, n= 3 O, n= 2

Figure out the number of valence electron/s to know how many electrons will take

part in the chemical reaction.Mg = 2 and O = 6

Check the electronegativity value to figure out which one is electropositive element

and vice versaMg = 1.2 and O = 3.5

From the electronegativity value you are now clear which element will give up

electrons and vice versa

Mg is electropositive so it will give up electron and becomes cation.

O is electronegative so it will accept up electron and becomes anion.


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Balance the reaction. In this case Mg needs to give up two electrons and O need

two electrons. So it will be a reaction between one magnesium atom and one

oxygen atom.

Q2. Describe the intermolecules bonding of water.

Steps to draw orbital model:

After you have worked out the intramolecules bonding between H and O in water,

youll get a model that looks like this.

Check the electronegativity value to figure out whether it is a polar or non-polar

covalent bonding. Electronegativity value for Hydrogen is 2.1 and that of oxygen is

3.5. Therefore the bonding is a polar covalent bonding meaning Oxygen because

of its greater tendency to attract electron will be slightly electronegative (-) and

hydrogen will be slightly electroposistive (+)

Now we now that bonding between water molecules will takes place when the - O

is attracted to + hydrogen from another water molecules and vice versa. This is


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how all the water molecules are attracted to each other and the bonding is known

as hydrogen bonding.

tutorial_i-2_atomic_structure_and_bonding.pdf

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