Okay, listen, the book says use the 'n+l' rule and memorize the sequence: 1s, 2s, 2p... But honestly? For boards, just remember sulphur (Z=16) is 2,8,6 and calcium (Z=20) is 2,8,8,2. Valency follows the octet rule—sulphur needs 2 electrons (valency 2), calcium can lose 2 (valency 2). My life says the specific thing is this sticky note on my chemistry book, right next to my baahni's case, with these two configurations circled. My adda friends and I drilled this for three hours last night over bad canteen cha, because our sir said this is guaranteed to come. So just mug that up.
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