Question

Order the following atoms from smallest to largest, judging from their relative positions in the periodic table: \(\mathrm{Cs}, \mathrm{Fe}, \mathrm{Ti}, \mathrm{Hf}\)

Short answer

The order of atoms from smallest to largest judging by their positions in the periodic table is: \(\mathrm{Fe} \rightarrow \mathrm{Ti} \rightarrow \mathrm{Hf} \rightarrow \mathrm{Cs}\).

Step-by-step solution

Find the positions in the periodic table

We need to find out where the given elements, \(\mathrm{Cs}\), \(\mathrm{Fe}\), \(\mathrm{Ti}\), and \(\mathrm{Hf}\), are located in the periodic table. - \(\mathrm{Cs}\): Cesium is in Group 1 (Alkali metals) and Period 6. - \(\mathrm{Fe}\): Iron is in Group 8 (Transition metals) and Period 4. - \(\mathrm{Ti}\): Titanium is in Group 4 (Transition metals) and Period 4. - \(\mathrm{Hf}\): Hafnium is in Group 4 (Transition metals) and Period 6.

Comparing sizes

Keeping in mind that atomic size increases going down a group and decreases going across a period from left to right, comparing the elements in this order will allow us to find the smallest to largest: 1. Compare \(\mathrm{Fe}\) and \(\mathrm{Ti}\): They are both in Period 4, with \(\mathrm{Fe}\) in Group 8 and \(\mathrm{Ti}\) in Group 4. Since atomic size decreases from left to right, \(\mathrm{Ti}\) is larger than \(\mathrm{Fe}\). 2. Compare \(\mathrm{Cs}\) and \(\mathrm{Hf}\): They are both in Period 6, with \(\mathrm{Cs}\) in Group 1 and \(\mathrm{Hf}\) in Group 4. Since atomic size decreases from left to right, \(\mathrm{Cs}\) is larger than \(\mathrm{Hf}\). 3. Compare \(\mathrm{Ti}\) and \(\mathrm{Hf}\): They are both in Group 4, with \(\mathrm{Ti}\) in Period 4 and \(\mathrm{Hf}\) in Period 6. Since atomic size increases going down a group, \(\mathrm{Hf}\) is larger than \(\mathrm{Ti}\). 4. We already know \(\mathrm{Cs}\) is the largest atom among the elements given. Therefore: Cs > Hf > Ti > Fe So, the order of atoms from smallest to largest judging by their positions in the periodic table is: \(\mathrm{Fe} \rightarrow \mathrm{Ti} \rightarrow \mathrm{Hf} \rightarrow \mathrm{Cs}\).

Key concepts

Atomic Size

Atomic size, or atomic radius, refers to the distance from the nucleus of an atom to the outermost electrons. Generally speaking, atomic size changes in predictable ways across the periodic table due to the arrangement of electrons and the balance between protons and electrons. In general, in any given group or column in the periodic table, atomic size increases as you move down. This is because the number of electron shells increases, which results in atoms with a larger radius. Conversely, across any given period or row, atomic size tends to decrease as you move from left to right. This happens because the number of protons in the nucleus increases across a period, which pulls the electrons closer to the nucleus, reducing the size of the atom.

Groups in Periodic Table

The periodic table is divided into vertical columns known as groups. Each group contains elements that have similar chemical and physical properties. One of the defining characteristics of elements within the same group is their valence electron configuration, which determines their chemical reactivity and bonding behavior. For example,

• Group 1: Known as the alkali metals, these elements like cesium (\(\text{Cs}\)) are highly reactive and have one valence electron.
• Group 4: Contains transition metals like titanium (\(\text{Ti}\)) and hafnium (\(\text{Hf}\)), which often display characteristic metallic properties.
• Group 8: Includes the iron (\(\text{Fe}\)), showing its placement among transition metals known for their strength and ability to form various alloys.

Understanding groups helps predict how elements will interact and react with one another.

Elements Position

The position of an element in the periodic table provides essential information about its properties and behavior. Each element is situated at the intersection of a specific group and period, which reveals not just its atomic characteristics but also potential chemical behaviors.- **Periods:** The horizontal rows in the periodic table are called periods, and they indicate the number of electron shells an atom has. For instance, titanium (\(\text{Ti}\)) and iron (\(\text{Fe}\)) are both found in Period 4, meaning they each have four electron shells.- **Groups:** Each vertical column or group signifies the number of electrons in the outermost shell, affecting the atom's reactivity. Thus, cesium (\(\text{Cs}\)) in Group 1 behaves differently than hafnium (\(\text{Hf}\)) in Group 4.Recognizing the element's position helps in predicting not only atomic size but also reactivity and bonding nature.

Trends in Periodic Table

The periodic table is a powerful tool for understanding the properties of elements due to periodic trends that exist within its structure. These trends arise from the arrangement of elements based on their atomic number and electron configuration. Some critical trends include:

• **Atomic Size Trend:** As discussed, atomic size increases down a group and decreases across a period from left to right.
• **Electronegativity:** This measures an atom's ability to attract electrons. It generally decreases down a group and increases across a period due to increased nuclear charge.
• **Ionization Energy:** The energy required to remove an electron also trends in the same direction as electronegativity.

These predictable patterns allow chemists to infer how an element might react or bond with others, simplifying the understanding of complex chemical behaviors by relating them back to this fundamental organization.