1. List the elements of the 3 rd period of the Periodic Table (excluding transit
ID: 480281 • Letter: 1
Question
1. List the elements of the 3rd period of the Periodic Table (excluding transition metals) in the exact order of increasing first ionization energy.
2. List the elements of the 3rd period of the Periodic Table (excluding transition metals and Ar) in the order of increasing atomic radius.
3. List the elements of the 3rd period of the Periodic Table (excluding transition metals and Ar) in the order of increasing electronegativity.
4. Arrange the following elements (Na, Mg, Al, Si, and P) in the order of increasing electrical conductivity.
Explanation / Answer
Period 3 elements are :
Na Mg Al Si P S Cl Ar
1]
Ionisation energy increasing order
Na < Al < Mg < Si < S < P < Cl < Ar
Mg > Si
Because in Mg --- 3s2 orbital is completely filled where as in Al - 3p1 orbital is present
. So it needs more energy to remove electron from Mg
P > S
Because in P - 3p3 orbital is partially filled whereas in Sulphur - 3p4 configutration
So more energy is needed for P to remove electron
2] Atomic radius trend
Na >Mg > Al > Si > P > S> Cl
From sodium to chlorine, the bonding electrons are all in the 3-level, being screened by the electrons in the first and second levels. The increasing number of protons in the nucleus as you go across the period pulls the bonding electrons more tightly to it. The amount of screening is constant for all of these elements.
3] Electronegativity
Na < Mg < Al < Si < P < S < Cl
As you go across the period, the bonding electrons are always in the same level - the 3-level. They are always being screened by the same inner electrons.
All that differs is the number of protons in the nucleus. As you go from sodium to chlorine, the number of protons steadily increases and so attracts the bonding pair more closely.
4] Electrical conductivity
Electrical conductivity increases from sodium to aluminium, then decreases to silicon. The remaining elements have negligible conductivity
P < Si < Na < Mg < Al
Na , Mg , Al --are all metals. They have metallic bonding, in which positive metal ions are attracted to delocalised electrons. The delocalised electrons are free to move and carry charge.
Si - Semi conductor - because the four outer electrons in each atom are held strongly in covalent bonds .
On increasing temperature , more electrons are promoted to higher enerhy levels and get delocalised .
P - Non-metal - the outer electrons are not free to move and carry charge because they are held strongly in covalent bonds
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