1. **State the problem:** We need to calculate the density of lead in SI units (kilograms per cubic meter) given its mass and volume. 2. **Formula for density:** Density $\rho$ is defined as mass divided by volume: $$\rho = \frac{m}{V}$$ where $m$ is mass and $V$ is volume. 3. **Convert given units to SI units:** - Mass: $23.94$ g $= 23.94 \times 10^{-3}$ kg $= 0.02394$ kg - Volume: $2.10$ cm$^3$ $= 2.10 \times 10^{-6}$ m$^3$ 4. **Calculate density:** $$\rho = \frac{0.02394}{2.10 \times 10^{-6}}$$ 5. **Simplify the expression:** $$\rho = \frac{0.02394}{2.10 \times 10^{-6}} = \frac{0.02394}{0.00000210}$$ 6. **Perform the division:** $$\rho = 11400$$ 7. **Final answer:** The density of lead in SI units is $$\boxed{11400 \text{ kg/m}^3}$$ This means lead has a density of 11400 kilograms per cubic meter.