1.On the periodic table, what is a period? What characteristic is shared by elements in the same period?

In our modern periodic table, the horizontal rows are known as periods , and the elements belonging to same period have same numbers of shells .

for example :

lithium, beryllium , boron , carbon , nitrogen , oxygen, fluorine and neon are in same period and have total 2 shells .

answersilicon (si); oxygen (o);