## Periodic Table Exam2 and Problem Solutions

**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 3^{rd} 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

**Solution:**

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 3^{rd }period and it has following electron configuration;

**Z: **1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}

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;

**Y: **1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}

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;

**Z: **1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}

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

**Solution:**

**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 _{4}X, _{9}Y, _{17}Z?

**I.** X and Z are in same group elements

**II.** X and Y are same period elements

**III. **X and Z form ionic compound

**Solution:**

We first write electron configuration of elements to find group and period numbers.

_{4}X: 1s^{2}2s^{2}

_{9}Y: 1s^{2}2s^{2}2p^{5}

_{17}Z: 1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}

**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

**Solution:**

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 2p^{6}. Which one of the following elements have similar chemical properties with X element?

**I.** _{8}Y

**II.** _{20}Z

**III. _{ }**

_{4}T

**Solution:**

Electron configuration of X^{+2} ion;

X^{+2}: 1s^{2}2s^{2}2p^{6} (X gives 2 electrons)

X: 1s^{2}2s^{2}2p^{6}3s^{2} ( X is in II A group)

Elements in same groups show similar chemical properties. Now we find group numbers of given elements;

_{8}Y: 1s^{2}2s^{2}2p^{4} (Y is in VI A group)

_{20}Z: 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2} (Z is in II A group)

_{4}T: 1s^{2}2s^{2} (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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