Question

Which elements are alkali metals? (a) scandium (b) iron (c) potassium (d) lithium (e) cobalt

Short answer

(c) Potassium and (d) Lithium are alkali metals

Step-by-step solution

Understanding Alkali Metals

Alkali metals are elements found in group 1 of the periodic table. They have one electron in their outermost shell and are highly reactive, especially with water. These metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

Identifying Alkali Metals in the Options

By referring to the periodic table, check each element in the options provided and determine if it belongs to group 1, thus identifying if it's an alkali metal.

Matching the Options with Alkali Metals

Match the elements listed in the options with the characteristics of alkali metals from step 1. (c) Potassium and (d) Lithium are alkali metals, while the other elements belong to different groups and are not alkali metals.

Key concepts

The Periodic Table and Its Groups

Imagine a vast library where all the elements are books sorted by similarities and properties. This library is known as the periodic table, and it's an essential tool for chemists and students alike. Arranged by atomic number, the periodic table groups elements that share characteristics, making it easier to predict their behaviors and how they might interact with other elements. The most left-hand column of the periodic table is like the first aisle of our library, reserved for a unique family of metals known as alkali metals.

These metals, including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr), all reside in group 1. Each row of the table introduces new 'shelves' with different 'books', or in our case, elements moving progressively into new periods with increasing atomic numbers. Every element on the same 'shelf', in this case, in the same group, shares a similar chemical profile which is handy when solving exercises regarding element groups like the one with alkali metals.

Chemical Reactivity of Alkali Metals

The chemical reactivity of an element describes how readily it forms chemical compounds with other elements. It's like how likely it is that an element will 'make friends' with others. Alkali metals are the life of the chemical party; they're incredibly eager to react, especially with water, to form new substances.

Why so reactive? Their willingness stems from having one electron in their outermost shell, which they can 'lose' easily. This one valence electron is like a loose single dollar bill; it's easy to spend. What happens in a reaction involving an alkali metal? They tend to donate this electron to another element, preferring to achieve a stable electronic configuration. This donation often results in the release of energy, sometimes explosively. For instance, when potassium (K) reacts with water, it quickly liberates hydrogen gas and heat, which can ignite the gas. Important safety note: This is why alkali metals should be handled with care in chemistry labs!

Electron Configuration in Alkali Metals

At the cue of electron configuration, imagine each element as a house with rooms for electrons. The structure of these 'homes' deeply influences the element's behavior. Alkali metals have a peculiar architectural style — their electron 'homes' have just one electron in the outermost 'room' or shell.

This characteristic layout corresponds to the notation ns¹, where 'n' indicates the period (or 'floor') the element is on in the periodic table. For example, lithium (Li) has an electron configuration of 2s¹ because it's on the second period and has one electron in its 's' orbital. This single electron defines their family trait, making them distinct in their reactions and properties. When solving exercises, it's crucial to recognize this configuration because it directly correlates with the element's placement in group 1 of the periodic table and thus determines its identity as an alkali metal.