How are the elements arranged on the periodic table?

They are arranged by increasing atomic mass/number. Atomic mass/number is identified by the amount of protons in the element. For example, Helium has an atomic mass of 2. That means it has 2 protons. Groups are identified when elements have similar properties, and periods are the rows of elements with the same number of electron shells.

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acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

where are the choice options?