sample questions 1.2

(answers are at the bottom)

1. Which is the atomic number and what does it tell us?

2. How can I tell how many neutrons an atom has by looking at the periodic table?

3. Why do atomic weights have decimal points?

4. How can you tell how many electrons the element of silver (Ag) has?

5. A neutral atom of Mercury (Hg) has an atomic weight of 201 and contains 80 electrons. Determine how many protons and neutrons it has, then write it out using the subscript/superscript format.

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ANSWERS

1. the atomic number is the one on top of the letter and it gives us the number of protons in an atom.

2. if you subtract the atomic number from the atomic weight, the number you get is rounded (up or down) to the nearest number. This final number tells you how many neutrons you have.

3. Because each element has the exact same number of protons in all its atoms but different number of neutrons. So scientists have determined the average number of neutrons in an element and this gives us an average number with decimal points. Therefore the atomic weight is derived from the average number of neutrons that present in a type of atom.

4. Look up its atomic number (47, which is the number of protons it has) and then, if there is no charge on the atom, you know you have the same number of electrons as protons. So the answer would be 47.

5. If the Mercury (Hg) atom is neutral, it has the same number of electrons as protons. Therefore, if it has 80 electrons, it must have 80 protons. Remember that  the atomic weight minus the atomic number (number of protons) gives us the number of neutrons in an atom. So, if the atomic weight is 201, we subtract 80 and get the number 121. Mercury has 121 neutrons. And in the subscript/superscript format, it would be written as:

Hg subscript superscript

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