Download Science 2nd prep. 1st term Lesson 2 Graduation of the properties of

Science 2nd prep. 1st term
Lesson 2
Graduation of the properties of Elements
in the Modern periodic table
we will study the graduation of some properities of the periodic table.
1-Atomic size
2-Electronegativity
3-Metallic and nonmetallic property
۞1-Atomic size property
Think carefully with your colleagues in the co-operating
group (fgure 1) and record
: your observations on the following questions
What do you observe for the graduation of the values of
the atomic size of elements in relation
? to the increasing of the atomic number
In periods ………………………………………
In groups •………………………………………
The atomic size evaluated in the bicometre = 1 / 1000000000000
»Bicometre = part of a million of a million of metre«
From the previous, we conclude that
1- In period
The atomic size of the same
period decreases by the increase
of their atomic numbers(G.R.?)
2- In group
The atomic size of the same group
increases by the increase of their
atomic numbers(G.R.?)
Due to The increase of the
attraction force between positive
nucleus and the electrons in the
outermost energy level
due to the increase of the number of
the energy levels in the atoms
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Science 2nd prep. 1st term
2-The electronegativity property
observe and think carefully with your classmates
and record your observations on the following questions:
What do you observe for the graduation of values
of the electronegativity of elements
by increasing the atomic number ?
• In periods....................................................................................
• In groups....................................................................................
Electronegativity values of some elements.
electronegativity??!
From the previous, we can conclude that :
1- In period
By increasing the atomic number the
electronegativity of elements of the
same period increases
2- In group
but it decreases in the same group.
The electronegativity of fourine element
is the highest value and equals 4
The polar compounds
To understand the concept of the polarity of some chemical compounds, you can do the
following activity
Activity(3)
Determination of the properties of the polar compounds.
For the illustrated elements in it (Use fgure 2)
• Oxygen and hydrogen in H2O molecule.
• Nitrogen and hydrogen in NH3 molecule.
............................................................................
the electrons of the bond
towards itself in :
(A) Molecule of water H2O .
(B) Molecule of ammonia NH3 .
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Science 2nd prep. 1st term
from the previous we can consider that :
1-The polar compound is a covalent compound, the electronegativity
difference between its elements is relatively high.
2-Water molecule and ammmonia molecule are from
examples of polar compounds
The difference in electronegativity of the elements in the molecule has an important role in
determining the type of link between the two chemical bonds
1 - link hydrogen atoms with oxygen atoms to form water molecule H2O
The ability of the oxygen atom to attract e-covalent bonds (OH) is greater than the
capacity of the hydrogen atom because the electronegativity of oxygen (3.5) is greater
than Alsalbeh hydrogen (2.1)
Water from the polar covalent compounds, because difference electronegativity
3.5-2.1 = 1.4
2 - Engagement nitrogen atom with three atoms of hydrogen to form
ammonia molecule NH3
The ability of the nitrogen atom to attract e-covalent bonds (NH) is greater than the
capacity of the hydrogen atom as the electronegativity of nitrogen (3) greater than
Alsalbeh hydrogen (2.1)
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Science 2nd prep. 1st term
Ammonia compounds polar covalent because difference electronegativity 3-2.1 = 0.9
3 The metallic and nonmetallic property:
– Elements are divided into 4 main kinds, which are :
☼ Metals.
☼ Nonmetals.
☼ Semimetals (Metalloids).
Metals
☼ Inert gases.
Nonmetals
are characterized by that their outermost
shells contain less than (4) electrons
are characterized by that their
outermost shells contain more than (4)
electrons and less than(8)
tend to lose these electrons during the
chemical reaction To reach the nearest inert
gas preceding them in the periodic table.
tend to gain electrons during the chemical
reaction. To reach the nearest inert gas
next them in the periodic table,
forming positive ions.
forming negative ions
Semimetals (Metalloids).
They are the elements which have the properties of both metals
and nonmetals.
are characterized by that their outermost shells contain (3 to 6)
electrons
It is diffcult to identify semimetals by knowing their electronic
confguration due to the difference of numbers of the electrons in
theirvalencies shells as shown in the table:
Activity
Discovering the graduation of the metallic and
nonmetallic properties in the periodic table.
From the previous, we can conclude :
1- The period starts with strong metal, as the atomic number increases in the same
period the metallic property decreases gradually until we reach semimetals and
then nonmetals start appear and as the atomic number increases, the nonmetallic
property increases until we reach the strongest nonmetal in group 7A.
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Science 2nd prep. 1st term
2- Metallic property of the same group increases by the increase of the atomic number
as we go from up to down (as in group 1A) due to the increase of the atomic size, while
nonmetallic property decreases (as in group 7A) due to the decrease of electronegativity
values.
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Science 2nd prep. 1st term
Questons on lesson 2
1 – in the same period,the element which has th highest electronegativity lies in group
………………
a. 1A
b. 2A
c.7A
d. 0
2 – the electronegativity for 19K element is ……………… the electronegativity for 11Na
element
a. greater than
b. smaller than
c. equal to
d. no correct answer
3 – the electonegativity of fluorine equals ……………….
a. 2.1
b.4
c. 5
d. 6
4 – which of the following elements is a metallic element? ………………..
a. 12Mg
b. 17Cl
c. 8O
d. 10 Ne
5 – An element (x) its atomic number is 13 so,the mumber of electrons in its ion is ………..
a. 8
b. 10
c. 11
d. 12
6 – all the following elements are metalloids except …………….
a. terllium.
B. silicon.
C. boron.
D. bromine.
7 – each period in the periodic table starts with …………………
a. metal .
b. metalloid
c. nonmetal.
D. inert gas.
8 - ………………. Is the least metallic element in group (1A)
a. Na
b. Cs
c. K
d. Li
9 – the nonmetallic property decreases gradually within group (7a) as we go from ………….
a. left to right.
B. right to left
c. top to bottom.
D. bottom to top.
Complete the following statements:
1 – by increasing the atomic number, the values of atomic sizes …………….. in the periods
of the periodic table.
2 – by increasing the atomic number in groups, the atomic size ……………… due to the
increase of the mumber of ……………
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Science 2nd prep. 1st term
3 – the element (8x) has ………. atomic size than element (6Y).
4 – by increasing the atomic number, the values of electronegativity ………. In the groups
of the periodic table.
5 – the electronegativity in the modern periodic table increases from …………..to …………….
Inside the same period.
6 – in period (2) the electronegativity of oxygen (8O) is ………….. than that of mitrogen
(7N).
7 – the polarity of water is ………………. Than that of ammonia as the difference in
…………………. Between elements of water is ……………. Than that between elements of
ammonia.
8 –the elements are classified into four main kinds which are metals, nonmetals, …………
and …………………..
9 – the last level of metallic elements contains ………………… than four electrons , while
that of nonmetallic elements contains ……….. than four electrons.
10 – the ………..ion carries a number of ……………… equals the mumber of lost electrons.
11 - ……………….. and ………………… are examples of metalloids.
12 – by increasing the atomic number within a period, the metallic property …………….,
while the nonmetallic property ……………
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