Helpp plss! As you move from left to right across a period, what happens to the atomic radii? They increase, because of the higher number of occupied energy levels.
They increase, because of the weaker attraction of electrons to the nucleus.
They decrease, because of the stronger effective nuclear charge.
They decrease, because of the increased atomic mass.

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Explanation:

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

it's all four options.