Which two statements are true about a system

The answers are both A system is a group of objects analyzed as one unit.

 Energy that moves across system boundaries is conserved

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since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

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