Periodic Table Exam2 and Problem Solutions
1. First ionization energies vs. atomic mass graph of X, Y, Z, T and R is given below.
If Z is in 3rd period, which one of the following statements is false?
I. Atomic number of X is 16
II. Y is in p block
III. Z and T are in same period
IV. Electron configuration of R shows spherical symmetry property
Since change in the first ionization energy of Z and T are too high, Z is noble gas and T is in I A group. Thus, Z is noble gas in 3rd period and it has following electron configuration;
Atomic number of Z is 18
I. Atomic number of X = Atomic number of Z - 2
Atomic number of X is 16. I is true
II. Y has atomic number 17 and has following electron configuration;
As you can see Y is in p block. II is true.
III. Z is in 3rd period but T is in fourth period. III is false.
IV. Electron configuration of R is given below;
Since all orbitals are filed, R shows spherical symmetry property. IV is true.
2. Which one of the following statements is false for elements given in the periodic table?
I. Electron affinity of Y is larger than others
II. X and T share electrons and form compound.
III. Z has largest atomic radius
IV. Ionic property of ZY compound is larger than others
I. Electron affinity increases as we move from left to right and top to bottom in periodic table. Thus, Y has larger electron affinity, I is true.
II. Since X is in I A group, it is metal and T is in VA and nonmetal. So, X and T can form compound by electron transfer, not by electron sharing. II is false.
III. Atomic radii increases as we move from right to left and top to bottom in periodic table. So, Z has largest atomic radii, III is true.
IV. Increasing in the electronegativity increases ionic property of compounds. Electronegativity increases from left to right and decreases from top to bottom in periodic table. Z is the one having smallest electronegativity and K is the one having highest electronegativity. Difference between electronegativities of these elements make compound have largest ionic property. IV is true.
3. Which ones of the following statements are true for 4X, 9Y, 17Z?
I. X and Z are in same group elements
II. X and Y are same period elements
III. X and Z form ionic compound
We first write electron configuration of elements to find group and period numbers.
I. Number of electrons in last shell orbitals give group number;
Y and Z are in VII A group. I is true
II. Last shell number gives period number. So, X and Y are in second period. II is true.
III. Since X is in II A group it is metal and Y is in VII A group and it is nonmetal. Property of compound is ionic. III is true.
4. Which ones of the following statements are always true related to periodic table?
I. s and d block elements are all metal
II. p block elements are nonmetal and noble gases
III. There are nonmetals before noble gases.
IV. There are halogens before noble gases
H is in I A group but it is not metal. I is false.
p block elements are metals, nonmetals and noble gases. II is false
When we examine periodic table we see that there are always nonmetals before noble gases. III is true.
H comes before He and it is not halogen. Thus, IV is false.
5. Electron configuration of X+2 last with 2p6. Which one of the following elements have similar chemical properties with X element?
Electron configuration of X+2 ion;
X+2: 1s22s22p6 (X gives 2 electrons)
X: 1s22s22p63s2 ( X is in II A group)
Elements in same groups show similar chemical properties. Now we find group numbers of given elements;
8Y: 1s22s22p4 (Y is in VI A group)
20Z: 1s22s22p63s23p64s2 (Z is in II A group)
4T: 1s22s2 (T is in II A group)
Z and T are in same group with X, thus they have similar chemical properties.
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