Question

these four elements are all in the same horizontal row (period) of the periodic table. what is the same about electron shells for elements in the same period? what is different about the electrons in the outer shell for elements in the same period?

Explanation:

• For elements in the same period (horizontal row) of the periodic table:
• Same about electron shells: They have the same number of electron shells. For example, all elements in period 2 have 2 electron shells.
• Different about outer - shell electrons: The number of electrons in the outer shell (valence electrons) increases from left to right across the period. For instance, in period 2, lithium (Li) has 1 valence electron, beryllium (Be) has 2, and so on until neon (Ne) which has 8 valence electrons.

Answer:

• Same: The number of electron shells.
• Different: The number of electrons in the outer shell.