What is the main reason for the periodic trends in atomic size across a period? (Variant 9)Correct Answer: Increase in nuclear charge ! Other People SaidIncrease in the number of energy levels: 105 Increase in nuclear charge: 1001 Increase in electron repulsion: 98 Next Question: What is the main reason for the periodic trends in atomic size across a period? (Variant 10)Increase in the number of energy levelsIncrease in nuclear chargeIncrease in electron repulsion