Question

Make a simple sketch of the shape of the main part of the periodic table, as shown. (a) Ignoring \(\mathrm{H}\) and \(\mathrm{He}\), write a single straight arrow from the element with the smallest bonding atomic radius to the element with the largest. (b) Ignoring \(\mathrm{H}\) and He, write a single straight arrow from the element with the smallest first ionization energy to the element with the largest. (c) What significant observation can you make from the arrows you drew in parts (a) and (b)? [Sections \(7.3\) and 7.4]

Short answer

To demonstrate the trends in atomic radius and ionization energy in the periodic table, draw a straight arrow from the smallest bonding atomic radius (upper right) to the largest (lower left) and another arrow from the smallest first ionization energy (lower left) to the largest (upper right). The arrows have opposite directions, showing that as atomic radius increases, ionization energy decreases, and vice versa. This is due to variations in effective nuclear charge experienced by the outermost electrons of larger and smaller atoms.

Step-by-step solution

Draw the main part of the periodic table

Begin by drawing the main part of the periodic table, which contains groups 1 to 18 (excluding hydrogen and helium) and periods 2 to 7.

Identify Trends in Atomic Radius and Ionization Energy

The atomic radius generally decreases from left to right across a period and increases from top to bottom within a group. Thus, the elements with the smallest atomic radius can be found in the top right part of the periodic table, and the largest atomic radius can be found in the bottom left part. The ionization energy generally increases from left to right across a period and decreases from top to bottom within a group. Thus, the elements with the smallest ionization energy can be found in the bottom left part of the periodic table, and the largest ionization energy can be found in the top right part.

Draw an Arrow Representing Atomic Radii Trends

To represent the bonding atomic radius trend, draw a single straight arrow starting from the element with the smallest bonding atomic radius (top right corner) to the element with the largest bonding atomic radius (bottom left corner).

Draw an Arrow Representing Ionization Energy Trends

To represent the ionization energy trend, draw a single straight arrow starting from the element with the smallest first ionization energy (bottom left corner) to the element with the largest first ionization energy (top right corner).

Make a Significant Observation

You will notice that the arrows for atomic radii and ionization energy trends are in opposite directions, indicating that as atoms increase in size, the ionization energy decreases, and vice versa. This is due to the fact that larger atoms have more energy levels and electrons, reducing the effective nuclear charge experienced by the outermost electrons, making it easier to remove them and thus, reducing the ionization energy. On the other hand, smaller atoms have fewer energy levels and electrons, increasing the effective nuclear charge experienced by the outermost electrons, making it harder to remove them and increasing the ionization energy.

Key concepts

Atomic Radius

The atomic radius is an important aspect of understanding periodic trends. When you think about the atomic radius, imagine it as the size of an atom. How wide is it from one side to the other? It can be a little tricky to nail down because atoms are not solid spheres, but you can think of it as the distance from the center of the atom to the edge of the outermost electron cloud.

• Atomic radius decreases as you move from left to right across a period. Why? Because although the number of protons and electrons increase, electrons are added to the same energy levels. As protons increase in the nucleus, they pull more strongly on the electron cloud, making the atom smaller.
• Atomic radius increases as you move down a group. This happens because new energy levels are being added, making the atom larger, even though the increased number of protons should theoretically pull more on electrons.

You can picture this trend by drawing an arrow in your mind from the top right to the bottom left across the periodic table. Larger atoms are towards the bottom left.

Ionization Energy

Ionization energy is the amount of energy required to remove an electron from an atom. It's like the tug-of-war between the electrons orbiting an atom and the positively charged nucleus pulling them in. The strength of this pull is influenced by a couple of key factors.

• Ionization energy generally increases as you move from left to right across a period. This is because electrons are more strongly attracted to the nucleus due to the greater number of protons without a significant increase in shielding from inner electrons.
• Conversely, ionization energy decreases as you move down a group. This decrease occurs because the outermost electrons are further away from the nucleus and are therefore less strongly bound. Increased electron shielding also plays a role.

Visualize an arrow moving from the bottom left to the top right of the periodic table to understand where ionization energy is highest and lowest.

Periodic Table Structure

The periodic table is thoughtfully organized to showcase periodic trends and group similar elements together. Think of it as a map that helps us predict chemical behavior and properties.

• The horizontal rows are called periods. Moving across a period from left to right, You see changes in properties such as atomic size and ionization energy.
• The vertical columns are called groups or families. Elements belonging to the same group often share similar chemical characteristics due to having the same number of valence electrons.
• This organization reveals seamless patterns - for instance, metals are positioned on the left; non-metals are mostly on the right, interrupted by metalloids forming a stairstep between the two.

In essence, the periodic table's structure is your gateway to understanding the logical patterns governing the behavior of elements.