Port Said International Schools
Better Education for Future Generations
Science Department
Grade: 11
Unit 2 Lesson 2
Name: ………………………………………. Date: ……………………………………………………
Write the scientific term for each of the following:
1. Half the distance between the centers of two similar atoms in a diatomic molecule.
"2nd session 07".
Atomic radius
2. The distance between the nuclei of two bonded atoms.
Bond length
3. The amount of energy required to remove the most loosely bound electrons
completely from an isolated gaseous atom. "2nd session 04".
Ionization energy
4. The energy required to convert M+ to M++.
Second ionization energy
5. The tendency of an atom to attract the electrons of the chemical bond to itself. "1st
session 01".
Electronegativity
Choose the correct answer:
1. The biggest atom is size in a given period is that of (1A – 1B – halogens – 18)
group.
2. When a metal atom combines with a nonmetal atom to form a molecule, the bond
length equals the ……………… "2nd session 01"
a. Sum of the two atomic radii.
b. Sum of the two ionic radii.
c. Double the nonmetal radius.
d. Double of the metal radius.
3. The equation: X + e- → X- + energy represents ……
a. The electron affinity concept.
b. A chemical process whose ∆H is positive.
c. An endothermic process.
d. The first ionization energy concept.
4. The elements of the same group are similar in the (principal quantum number –
radius – number of electrons in outermost level – electronegativity).
5. The electronegativity of elements through the horizontal periods increases as
their…………..
a. Atomic radii increase.
b. Atomic number decrease.
c. Atomic radii decrease.
d. (a) and (b).
6. Halogens are characterized by (high electronegativity – small
atomic radii – high ionization energy – all the previous).
7. Three different elements, A, B and C in the same period and three
successive groups, if C is an inert gas, the symbol of A ion will be
(A+ - A++ - A- - A--).
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Port Said International Schools
Better Education for Future Generations
Science Department
Grade: 11
Unit 2 Lesson 2
Calculate the atomic radius of carbon atom providing that the bond length of chlorine
molecule Cl – Cl = 1.98° A, and the bond length between carbon and chlorine molecule
C-Cl = 1.76°A. "Aug. 97"
The atomic radius of chlorine = 1.98 ÷ 2 = 0.99
The atomic radius of carbon = 1.76 – 0.99 = 0.77
Calculate the bond length of the fluorine molecule providing that the bond length of the
hydrogen molecule H-H = 0.6°A, and the bond length of hydrogen fluoride molecule =
0.94°A. "1st session 02"
The atomic radius of hydrogen = 0.6 ÷ 2 = 0.3
The atomic radius of fluorine = 0.94 – 0.3 = 0.64
The bond length of fluorine = 0.64 × 2 = 1.28
Give reason for the following:
1. It is incorrect to define the atomic radius as the distance from the nucleus to the
farthest electron.
Because it hard to identify the location of the outermost electron precisely
2. The ionization potential decreases across the elements of the same group by
increasing the atomic number. "1st session 07"
Because as the atomic number increases the number of energy levels increase and the
attraction force between the nucleus and the valence electrons decreases so it is easy with
the least amount of energy to lose an electron
3. The ionization potential of 12Mg is less than that of 17Cl. "1st session 98".
Because as we move in through the period from left to right the atomic radius decreases –
the attraction force between the nucleus and the valence electrons increases and it is hard to
separate an electron from the atom
4. The 1st ionization energy of the Nobel gas is very high. "2nd session 08".
Because we break a complete and stable energy level
5. The electron affinity of fluorine is less that of chlorine although fluorine comes
before chlorine through halogens group. "1st session 03".
Because the size of fluorine is very small and as a result the repulsion force between the
electrons is very high so it is very hard for one more electron to be added
6. The electron affinity of group (18) elements has no value.
Because the outermost energy level is complete so the atom doesn’t need
to gain any electrons
http://pisscience.wikispaces.com/
Port Said International Schools
Better Education for Future Generations
Science Department
Grade: 11
Unit 2 Lesson 2
7. The abnormality of the electron affinity in 4Be and 7N.
In beryllium the outermost energy configuration is 2s2 (completely filled – more stable)
and in the case of nitrogen the electronic configuration of the outermost energy level is 2s2
2p3 (half filled – more stable)
What is meant by:
1. The atomic radius?
Half the distance between the centers of two similar atoms in a diatomic molecule
2. The bond length?
The distance between the nuclei of two bonded atoms .
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