4. explain why do elements in groups share more chemical properties than
elements in a period?

The tend to share the same number of outer electrons. Halogens, for example all have 7 outer electrons, and therefore there oxidation number is -1.

Explanation:

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.

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