How does the number of valence electrons for elements change across a period? the number decreases. the number increases. the number stays constant. the number increases and then decreases for noble gases

Option (b) is the correct answer.

Explanation:

Valence electrons is the number of electrons present in the outermost shell of an atom.

So, when we move across a period from left to right then there will be increase in number of valence electrons.

For example, valence electrons in carbon is 4, nitrogen has 5 valence electrons, oxygen has 6 valence electrons.

Thus, we can conclude that number of valence electrons increases for elements change across a period.

the answer is definitely c.