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Atoms
An atom’s atomic number has many uses. It tells you where to find it on the periodic table, obviously (hydrogen is 1 and
helium is 2), but it also tells you the number of protons found in the atom’s nucleus. If an atom is neutral (meaning it has a
charge of 0), then its number of protons (positive charged particles) must equal its number of electrons (negatively charged
particles). This is because the charges are added together (like –2 +2 =0) to find the overall charge.
1. So, if hydrogen has 1 proton (that’s +1), how many electrons must it have to have a neutral charge?
2. Lithium has 3 protons. How many electrons does it need to have a charge of 0?
The mass number of an atom is equal to the number of protons and neutrons it holds in its nucleus.
Mass # =Protons + Neutrons
So, the bulk of the mass of an atom is found in its nucleus. So, if Hydrogen has a mass number of 1 and atomic number of
1, then it has 0 neutrons. It will have 1 proton to account for its mass number. An atom can lose or gain electrons to alter
its charge and it can have different numbers of neutrons to change its mass, but the number of protons is always equal to its
atomic number. On the other hand if Hydrogen has a mass number of 3, then because its atomic number is 1, it will have 1
proton, 1 electron (to equal the positive charge and make its overall charge 0), and 2 neutrons.
So, tell me how many protons, neutrons, and electrons are in the following:
3.
Lithium—8
4.
Sodium—23
5.
Boron—11
6.
Fluorine—18
7.
Sulfur—32
8.
Gallium—70
9.
Calcium—41
10. Radon—222
In biology, we focus primarily on organic compounds that include elements such as hydrogen, carbon, nitrogen, and
oxygen. So, how many protons, neutrons and electrons are in the following?
11. Oxygen—16
12. Nitrogen—14
13. Carbon—12
14. Hydrogen—3 (its sometimes called tritium)