Comparing Group 1 & Transition Metals

Physical Properties

Group 1 metals (alkali metals) and transition metals differ significantly in their physical properties:

• Density: Transition metals generally have much higher densities than Group 1 metals. For example, iron (a transition metal) has a density of about 7.9 g/cm8, whereas potassium (a Group 1 metal) has a density of only about 0.86 g/cm8. This is because transition metals have more closely packed atoms and heavier atoms.
• Melting and Boiling Points: Transition metals have high melting and boiling points due to strong metallic bonding involving their d-electrons. Group 1 metals have relatively low melting and boiling points that decrease down the group. For instance, lithium melts at 1806C, while iron melts at 15386C.
• Hardness and Strength: Transition metals are typically hard and strong metals, making them useful for construction and manufacturing. Group 1 metals are soft and can be cut easily with a knife. For example, sodium is soft, while copper is hard and malleable.

For instance, irons high melting point and hardness make it suitable for building structures, whereas sodiums softness and low melting point mean it is stored under oil to prevent reaction with air.

Chemical Reactivity

The chemical reactivity of Group 1 metals and transition metals also shows clear differences:

• Reactivity with Water: Group 1 metals react vigorously with water, producing hydrogen gas and a metal hydroxide. The reaction becomes more vigorous down the group. For example, potassium reacts explosively with water, while lithium reacts more gently. Transition metals generally do not react with water easily.
• Reactivity with Oxygen: Group 1 metals react quickly with oxygen to form metal oxides, often producing colourful flames. Transition metals react more slowly with oxygen, forming metal oxides that are often used as protective coatings (e.g., iron rusts slowly).
• Reactivity with Acids: Group 1 metals react readily with dilute acids to produce hydrogen gas and a salt. Transition metals also react with acids but usually less vigorously. Some transition metals, like copper, do not react with dilute acids easily.

For example, sodium reacts with dilute hydrochloric acid to form sodium chloride and hydrogen gas:

$$\text{2Na} + 2HCl \rightarrow 2NaCl + H_2$$

Electron Configuration and Ion Formation

The differences in electron configuration explain many contrasting properties between Group 1 and transition metals:

• Group 1 Metals: Have one electron in their outer shell (e.g., sodium: 2 8 1). This single electron is easily lost to form a +1 ion (e.g., Na).
• Transition Metals: Have electrons in d-sublevels, allowing them to show variable oxidation states (commonly +2 and +3, but others too). This means they can form ions with different charges, such as Fe and Fe.
• Formation of Ions: Group 1 metals form only one type of ion (+1), whereas transition metals can form multiple ions due to their variable oxidation states.

For example, iron can form Fe or Fe ions, which affects the colour and properties of its compounds.

Example: Sodium has the electron configuration 2 8 1. It loses one electron to form Na with configuration 2 8, which is stable.

Uses and Applications

The distinct properties of Group 1 and transition metals lead to different practical uses:

• Group 1 Metals: Used in batteries (e.g., lithium-ion batteries) and in compounds such as sodium chloride (table salt) and potassium compounds used in fertilisers.
• Transition Metals: Widely used as catalysts in industry (e.g., iron in the Haber process), and in alloys to improve strength and resistance (e.g., stainless steel contains iron, chromium, and nickel).

For example, lithium is used in rechargeable batteries due to its light weight and high reactivity, while iron alloys are used in construction for their strength.