To solve the problem we will use the following equation:
n(Li) = N(Li) / NA
n - the number of moles
N - the number of particles
NA - Avogadro's number that has following value: 6.022×10²³ mol⁻¹
From the upper relation follows:
N(Li) = n(Li) × NA
N(Li) = 1mole × 6.022×10²³ mol⁻¹ = 6.022×10²³ atoms of lithium