* Understanding the Formula: Na₂SO₄ represents sodium sulfate. The subscript "2" in Na₂ indicates that there are two sodium ions (Na⁺) for every one sulfate ion (SO₄²⁻).

* Moles to Ions: Since 1 mole of Na₂SO₄ contains 2 moles of Na⁺ ions, 0.5 moles of Na₂SO₄ will contain:

0.5 moles Na₂SO₄ * (2 moles Na⁺ / 1 mole Na₂SO₄) = 1 mole Na⁺

* Avogadro's Number: To find the number of sodium ions, we use Avogadro's number (6.022 x 10²³ ions/mole):

1 mole Na⁺ * (6.022 x 10²³ ions/mole) = 6.022 x 10²³ Na⁺ ions

Therefore, there are 6.022 x 10²³ sodium ions present when 0.5 moles of Na₂SO₄ is dissolved in water.