问题
选择题
下列价电子排布式表示的四种元素中，电负性最大的是
A．4s1
B．2s22p5
C．3s23p4
D．3d64s2
答案
答案：B
题目分析：由价电子排布式可知，四种元素分别是K、F、S、Fe，电负性最大的是F。
点评：电负性最大也即是吸电子能力最强，解题的技术是结合选项，吸电子能力越强，电负性越强。
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下列价电子排布式表示的四种元素中，电负性最大的是
A．4s1
B．2s22p5
C．3s23p4
D．3d64s2
答案：B
题目分析：由价电子排布式可知，四种元素分别是K、F、S、Fe，电负性最大的是F。
点评：电负性最大也即是吸电子能力最强，解题的技术是结合选项，吸电子能力越强，电负性越强。
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| Many people find that regular physical activity gives them an unexpected benefit. They sleep better and wake up feeling more 1 , in part due to increased amounts of deep sleep. Deep sleep may play a role in the body restoring (恢复) itself 2 , as opposed to REM (rapid eye movement) or dreaming sleep. Researchers have found that physical exercise, especially 3 in the afternoon or early evening, produces more 4 early in the night. 5 can also help you get a better night's sleep in a number of indirect ways. The relaxation and tiredness 6 by exercise can improve sleep. Exercise encourages weight loss and also may 7 depression. Exercising later in the day can also help delay the 8 drop in your body's temperature. The 9 of exercise are especially important for older people, 10 exercise has been shown to increase the amount of sleep senior adults get in a night and reduce the time it takes to fall asleep. But be sure you finish exercising at least 4 hours before bedtime-working out later than that could leave you too excited to fall asleep easily. | ||||
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