The alkaline earth metals have similar chemical properties because________?

Analyze the question: It asks why alkaline earth metals (Group 2: Be, Mg, Ca, Sr, Ba, Ra) show similar chemical properties.

Concept: The chemical properties of an element are determined mainly by the number of electrons in its outermost shell (valence electrons). Elements in the same group of the periodic table have the same number of valence electrons, so they react in similar ways.

Solution:

• Group 2 elements all have 2 valence electrons (configuration ns²). • Be: 2,2 • Mg: 2,8,2 • Ca: 2,8,8,2
• Each one tends to lose these 2 electrons to form a 2+ ion (M²⁺), which gives similar reactions, such as forming oxides (MO), hydroxides (M(OH)₂) and chlorides (MCl₂).

Checking the options:

• A. Same period: Wrong. They are in the same group, not the same period. Elements in the same period have different properties across the period.
• B. Salts are colourless: This is a result of having no unpaired d electrons in their ions, not the cause of similar properties.
• C. Same number of valence electrons: Correct. This is the fundamental reason.
• D. Very reactive: This is a general description, not an explanation, and Be is not very reactive.

Answer: C

Tip: "Same group = same valence electrons = similar chemistry." Whenever a question asks why elements in a group behave alike, think of valence electrons. For "same period", think of the same number of electron shells.