9 2.4 The Periodic Trends

Figures

Figure 2.4.3: Ionisation Energy on the Periodic Table.

A diagram of ionisation energies across the s and p blocks of the periodic table, showing varying sizes of the atoms with spheres varying in size, corresponding with ionisation values. The spheres represent atoms, with helium in the top right corner with the smallest sphere size and highest ionization energy of 2372 kj/mol. Sizes increase as ionisation energy decreases towards caesium at the bottom left of the periodic table, with an ionisation value of 376 kj/mol. Notable exceptions are found within group 16, being Te and Po.

Figure 2.4.4: Electronegativity of elements

A diagram of s and p blocks of the periodic table displaying the electronegativity values of the elements. The diagram has two large arrows indicating increasing electronegativity in the periodic table—the first arrow begins at the top left and goes to the right; and the second arrow starts from the bottom left and goes vertical to the top of the table. The electronegativity values decrease from flourine in group 7A which has the highest electronegativity at 3.98; moves down to francium in group 1 with the lowest at 0.7. Noble gases do not have an electronegativity value.

Practice questions

Multiple choice questions

1. Predict which atom is larger for the following pair of atoms.
   1. C
   2. F
2. Predict which atom is larger for the following pair of atoms.
   1. Na
   2. Cs
3. In Figure 2.4.1, which element does not follow the standard atomic
   radius rule?
   1. I
   2. Te
   3. Xe
   4. Sb
4. Which of the following molecules has the greatest electronegativity?
   1. Na
   2. Cl
   3. B
   4. Ge

True/false question

1. Sodium has a greater atomic radius than chlorine; therefore, sodium has a higher ionisation energy.

Solutions

Multiple choice questions

1. (a).
   C Z= 6 and F Z= 9 are located in the second period. When moving across a period from left to right, atomic radii decrease as a result of increasing Z. C lies to the left of F in the same row. Therefore, C is larger than F.
2. (b).
   Na Z=11 and Cs Z=55 are located in group 1. Atomic radii increase from top to bottom of the periodic table as n increases. Cs is located below Na in the same column. Thus, Cs has a larger radius than Na.
3. (b).
   It has a higher atomic radius than Sb, which is further right on the table.
4. (b).

True/false question

1. False