Chemistry · Periodic Classification Of Properties · NEET
They are called "alkaline" because their oxides and hydroxides (like Ca(OH)2, lime) are basic (alkaline) in water. They are called "earth" because early chemists found their oxides in the ground and these oxides do not melt or dissolve easily. So the name mixes two old ideas: their oxides act as bases, and their oxides come from earth. For NEET, just remember Group 2 = alkaline earth metals = Be, Mg, Ca, Sr, Ba, Ra.
Every Group 2 element ends in ns², where n is the period number. Beryllium is [He]2s², magnesium is [Ne]3s², calcium is [Ar]4s², and so on. The two outer electrons are both in the s-orbital, which is why Group 2 is part of the s-block. NCERT even predicts that element Z = 120 (not yet made in bulk) would be in Group 2 with configuration [Uuo]8s². The ns² pattern is the single most tested fact about this group.
They have two loosely held electrons in the outer s-orbital. Both first and second ionization enthalpies are low enough that the metal gives up both electrons to reach the stable noble-gas configuration of the period before it. Losing two electrons leaves a full inner shell, which is very stable. So Ca becomes Ca²⁺, Mg becomes Mg²⁺, and so on. They never form +1 ions in normal compounds because the +2 state is far more stable.
Alkali metals are Group 1 (ns¹) and form +1 ions; alkaline earth metals are Group 2 (ns²) and form +2 ions. Group 2 metals are harder, denser, and have higher melting points than Group 1 because their +2 ions and extra bonding electron make stronger metallic bonds. Group 1 metals are more reactive than Group 2 because it is easier to lose one electron than two. Both are s-block and both get more metallic and more reactive going down the group.
They are in the s-block. The s-block holds Group 1 and Group 2 because their last electron enters an s-orbital. Group 2 elements end in ns², so the differentiating electron is an s-electron. Do not confuse this with the p-block (Groups 13–18) or the d-block. A common trap: helium also ends in s² (1s²) but is placed in the p-block with noble gases, so "ends in s²" alone does not always mean Group 2.
Going down Group 2 the metal becomes more electropositive and more metallic, so the oxides become more basic in this order: BeO < MgO < CaO < BaO. Beryllium is small and highly polarizing, so BeO has strong covalent character and behaves as amphoteric (reacts with both acids and bases). BeO is therefore the least basic / most acidic Group 2 oxide, while the rest are clearly basic. NEET 2018 asked exactly this: BeO is the most acidic oxide among BaO, BeO, MgO, CaO.
Ionic character of the hydrides increases down the group: BeH2 < CaH2 < BaH2. As the metal gets bigger and more electropositive down Group 2, its bond with hydrogen becomes more ionic. BeH2 is covalent (small, polarizing Be), while BaH2 is the most ionic. NEET 2018 tested this order directly.
Reactivity increases down the group. As you go down, atomic size grows and ionization enthalpy falls, so the outer 2 electrons are lost more easily. That is why Ca, Sr, and Ba react with even cold water to give hydrogen, while Be and Mg react much more slowly. Metallic character also increases down the group for the same reason.
Which of the following oxides is most acidic in nature?
Among CaH2, BeH2, BaH2, the order of ionic character is
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Radium is radioactive. Together they make up all of Group 2.
ns², where n is the period number. Example: Ca is [Ar]4s². The two outer s-electrons are lost to form +2 ions.
Because the last (differentiating) electron enters an s-orbital, giving the ns² configuration. Groups 1 and 2 together form the s-block.
NCERT predicts Z = 120 would be a Group 2 alkaline earth metal with configuration [Uuo]8s², following the same ns² pattern as the rest of the group.
Be and Mg are smaller and more polarizing, so they do not react with cold water and form more covalent compounds. Be especially shows a diagonal relationship with aluminium and gives an amphoteric oxide (BeO).
