What are the top three elements in the mantle?

Could you please elaborate on the top three elements in the mantle, as described in the paragraph? I'm curious to understand the significance and role of these elements within the mantle's overall composition and function. Could you provide a brief but comprehensive description of each, highlighting their unique characteristics and any interactions they may have with other components? I'm particularly interested in how these elements contribute to the mantle's overall effectiveness and performance. Thank you for your time and expertise in this matter.