1) Preheat oven to 375 degrees F. Cut whole chicken into thighs (leave drumsticks attached). Try to keep the breast whole with the bone-in. Also cut off the wings. So you should have 5 pieces: 2 wings, 2 thighs, 1 whole breast.
2) Toss chicken pieces with 2 tablespoons olive oil, chili powder, and a big pinch of salt and pepper.
3) Spread chicken pieces out on a sturdy sheet pan, skin side up. When oven is hot, bake chicken for 15 minutes.
4) Meanwhile, drain chickpeas and toss with 1-2 tablespoons olive oil, paprika, oregano, and a pinch of salt and pepper.
5) After 15 minutes, add chickpeas to the sheet pan, sprinkling them around the chicken pieces. Return to the oven and bake for another 20 minutes or so.
6) While sheet pan bakes, prep yogurt sauce and slice leeks. Add leeks to sheet pan after the 20 minutes are up and return to oven.
7) Bake chicken and sheet pan until chicken is cooked through on the thighs and breasts. Ideally, the breast should be 165 degrees F. in the thickest part. The thighs should be a bit hotter, maybe 175 degrees F. in the thickest part. In total, they will need 40-45 minutes total baking most likely.
8) When sheet pan is done, serve chicken and chickpeas over fresh arugula with yogurt sauce.