(1)同一周期元素从左到右元素的原子半径逐渐减小,同主族元素从上到下元素的原子半径逐渐增大,可知原子半径最大的是Na,最小的为H,
故答案为:Na;H;
(2)同周期元素从左到右,金属性逐渐减弱,同主族元素从上到下,金属性逐渐增强,则金属性最强的为K,与水反应最剧烈,
非金属性最强的元素为F,F 2 与水剧烈反应,
故答案为:K;F 2 ;
(3)同周期元素从左到右,非金属性逐渐最增强,同主族元素从上到下,非金属性逐渐减弱,则非金属性最强的为F,对应的氢化物最稳定,电子式为
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/5bafa40f4bfbfbed13d5280168f0f736afc31f3b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
,
故答案为:HF,
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/5bafa40f4bfbfbed13d5280168f0f736afc31f3b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
.