Barium

magnesium

calcium

what are their chemical properties

Explanation:

These are alkaline earth metals.

These are present in group two.

All have two valance electrons.

All alkaline earth metals form salt with halogens.e.g,

Mg   +   Cl₂    →    MgCl₂

Ba    +   Br₂    →     BaBr₂

Mg   +   Br₂    →     MgBr₂

Ca    +   Br₂    →     CaBr₂

They react with oxygen and form oxides of respective metal.

2Mg   +   O₂   →    2MgO

2Ba   +   O₂   →    2BaO

2Ca   +   O₂   →    2CaO

these oxides form hydroxide when react with water,

MgO  + H₂O   →  Mg(OH)₂

BaO  + H₂O   →  Ba(OH)₂

CaO  + H₂O   →  Ca(OH)₂

With nitrogen it produced nitride,

3Mg + N₂     →  Mg₃N₂

3Ba + N₂     →  Ba₃N₂

3Ca + N₂     →  Ca₃N₂

With acid like HCl,

Mg + 2HCl  →  MgCl₂ + H₂

Ba + 2HCl  →  BaCl₂ + H₂

Ca + 2HCl  →  CaCl₂ + H₂

gas

explanation:

smoke is the matter of a gas

i think it's letter a.