Which is true about each element in a period or horizontal row of the periodic table?

A.

Each element has one more outer shell than the element before it.

B.

Each element has one more outer electron than the element before it.

C.

Each element has one more isotope than the element before it.

D.

Each element bonds with the element before it.

The true about element in period or horizontal row of periodic table is

Each element has one more outer electron than the element before it. (answer B)

Explanation

In periodic table there are four horizontal rows (periods) that is period 1,2,3 and 4.

Across the period each element has one more electron than element before it.

For example Na and Mg which are in periodic 3.

Na has 2.8.1 or [Ne] 3s¹ electron configuration while Mg has 2.8.2 or [Ne] 3S² electron configuration.

Since Mg has 2 outer electrons while Na has 1 outer electron, Mg has more electron than Na.