Mass is measured in kilograms.
Protons and neutrons are in the center of the atom, making up the nucleus. The charge on the proton and electron are exactly the same size but opposite. Neutrons have no charge.
Answer:

Explanation:
Hello,
In this case, since the Lewis theory is based on the bonds formation between atoms via the valence electrons, we can verify the chemical formula of the compound formed by strontium and nitrogen by noticing that strontium has two valence electrons as it is in group IIA, for that reason, two nitrogens should be available for bonding. Therefore, since nitrogen is in group VA, it is said that three electrons are required to attain the octet (maximum amount bonded electrons), for that reason, three strontiums are should be available for bonding. In such a way, the formula should be:

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Answer:
Lead (II) Sulfate
Explanation:
Don't forget to add the (II) marking indicating that lead has a charge of 2+ (because Sulfate has a charge of 2-, balancing the ion).