Compare the inner core and the outer core?

The Earth's inner core is the Earth's innermost part and according to seismological studies, it has been believed to be primarily a solid ball with a radius of about 1220 kilometers, or 768 miles (about 70% of the Moon's radius). It is composed of an iron–nickel alloy and some light elements.
And he outer core of the Earth is a fluid layer about 2,300 km (1,400 mi) thick and composed of iron and nickel that lies above Earth's solid inner core and below its mantle. Its outer boundary lies 2,890 km (1,800 mi) beneath Earth's surface.