Chapter 3, Problem 1P

Before the element scandium was discovered in 1879, it was known as “eka-boron.” Predict the properties of scandium from averages of the corresponding properties of its neighboring elements in the periodic table. Compare your predictions with the observed values in Appendix F.

Interpretation Introduction

Interpretation:

The properties of scandium should be determined from the averages of the properties of neighbouring elements in the periodic table and predictions should be compared with the observed values in Appendix F.

Concept introduction:

The periodic table contains periods and groups. There are 18 groups and 7 periods in the periodic table. The vertical columns are known as groups and horizontal rows are known as periods.

The numbering of periods is done as 1 to 7 from top to bottom and groups are named as 1A, 2A, 3B to 8B, 1B, 2B, 3A to 8A from left to right where A represents representative elements and B represents transition elements. Elements in the same family have similar chemical and physical properties. In the periodic table, elements are classified as metals, non-metals or metalloids.

Answer to Problem 1P

Calculated values of Scandium are:

Melting point = 1250^oC

Boiling point = 2386^oC

Density = 3.02 g/cm³

The observed values and calculated values are nearer.

Explanation of Solution

Given information:

  

Scandium belongs to group 3 and period 4.The electronic configuration of scandium is: ${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}^{\text{6}}{\text{4s}}^{\text{2}}{\text{3d}}^{\text{1}}$ and number of electrons present in outermost shell is 3. It is present between calcium and titanium. Thus, the physical properties of scandium are equal to the average of the properties of calcium and titanium.

Melting point is calculated as = $\frac{\left(839+1660\right)}{2}$

= 1249.5^oC

Boiling point is calculated as = $\frac{\left(1484+3287\right)}{2}$

= 2386^oC

Density is calculated as = $\frac{\left(1.55+4.50\right)}{2}$

= $3.02{\text{ g/cm}}^3$

Now, from Appendix F:

Melting point of scandium = 1541^oC

Boiling point of scandium = 2386^oC

Density of scandium = 2.99 g/cm³

According to the calculated value and observed values, the physical properties are nearer but not exactly the same.