The number of Na atoms in the reactants = 2
Further explanation
Every chemical reaction involves compounds that can act as reactants or products
The reactants will react to produce products
The reactants are usually written on the left side of the reaction, while the products on the right side of the reaction
Reaction
2 NaCl + H₂SO₄ → 2 HCl + Na₂SO₄
The element with atomic number 11 = Na(Natrium)
The number of atoms of the element that reacts or is produced can be seen from the reaction coefficient and the number of atoms in the compound
Na in NaCl = 1 atom
From equation, cofficient for NaCl = 2, so number of atoms of Na=2 x 1 = 2