Question

1. justify why the number of valence electrons increases going across a period using electron configurations. as you go across a period the number of electrons a and the number of energy levels b. the valence electrons go into the c of the atom until the shell is full with d electrons (two electrons with hydrogen and helium).

Explanation:

• A: As we move across a period in the periodic table, the atomic number increases. Since the atomic number is equal to the number of electrons in a neutral atom, the number of electrons increases.
• B: The period number represents the principal energy level. All elements in a particular period have their valence electrons in the same principal energy level. So, the number of energy levels (principal energy levels for valence electrons) remains the same across a period.
• C: Valence electrons are added to the out - ermost shell (valence shell) of the atom as we move across a period.
• D: According to the octet rule (except for hydrogen and helium which follow the duet rule), the outermost shell (valence shell) is filled when it has 8 electrons.

Answer:

A. increases; B. remains the same; C. outermost shell; D. 8