1－18号元素，即氢、氦、钾、铰、硼、碳、氮、氧、氟、氖、钠、镁、铝、硅、磷、硫、氯、氖，它们的原子的核电行数分别为1到18。同学们若记住这些元素及顺序，意义重大。如记住镁为12号元素，则能推知，核外有12个电子；再根据核外电子排布知识可进一步推知，镁原子的核外电? Elements No. 1-18, ie, hydrogen, helium, potassium, hinge, boron, carbon, nitrogen, oxygen, fluorine, helium, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, helium, and the number of nuclear rows of their atoms 1 to 18 respectively. It is important for students to remember these elements and their order. If you remember that magnesium is the 12th element, you can infer that there are 12 electrons outside the nuclear; according to the knowledge of the nuclear electronic arrangement, you can further infer that the magnesium atom nuclear power?