This is an IMPERFECT CHIASM: when we love one another, God abides in us and perfects His love in us. The word Beloved appears in the two markers (verses 7A and 11A) which address us in a personal way.
1) The OPENING SUMMARY, verses 7 to 10, is an emphatic argument for the remaining verses 11 to 19. Verse 7B states we are called to love because God gave that provision. In order for God to abide in us and love one another, we must first know that Jesus's death for our sins was the complete love sacrifice for us. The a' element is an AMPLIFICATION of a, as is the b' element an AMPLIFICATION of b.
2) The two FRAME elements, verses 11B and 19, make a strong point to love one another. God loves us, so therefore we are called to do the same to others.
3) God's abiding love is stressed in the two B CORRESPONDING ELEMENTS. Our love is perfected when we love one another, for then God lives within us in His perfect love. With that love, we can have certainty of our judgment on that final day (verse 17A).
4) The C CORRESPONDING ELEMENTS are important statements for they confirm how we know that God lives within us. That is, the presence of the Holy Spirit assures us that we live with God: we in Him and He in us.
5) We know that the EXTRA D' element is emphatic because there is no similar text between verses 13 and 14. The emphasis stated in verse 16A that God not only loves us, He is love (see also verse 8). That statement, God is love, is widely quoted which should confirm the sense of emphasis in those two verses.
6) The two E CENTER POINT elements of the chiasm (verses 14 and 15) incorporate the power of testifying and confessing Jesus, thereby allowing God to abide in him and him in God.
7) The PARENTHESIS in verse 18 is a corollary about how fear from punishment inhibits the understanding of perfect love.