What caused the shielding effect to remain constant across a period

When moving from left to the right of a period, the number of electrons increases and the strength of shielding increases. As you move across period the number of shells remain same, the shielding effect will also remain constant.

Explanation:

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

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