| Course ID | Course | Professor | Time | Location |
| What is an atom | - |
What is an Atom?
- Nucleus, it is, depending on the element (see periodic table), of charged protons and uncharged neutrons. The charge of the proton is +1
- Electron: They oscillate around the nucleus and have the same charge as the proton, but with a negative sign -1
An atom whose charge is 0, contains exactly the same number of protons as electrons. The number of neutrons can vary, however. If this is the case, we speak of an isotope. A neutron or its mass is a little bigger than a proton. A neutron is neutral in charge, it does not Charge.
Atoms and molecules that have a charge are called ions. atoms or molecules of a positive charge, are called cations. Atoms and molecules, which are negatively charged, are anions.
The atomic theory of atome (Greek atomos) means indivisible. John Dalton developed the atomic theory: All atoms of the same element are the same. Atoms of different elements are not equal. When chemical reactions are taking place, the atoms are connected to each other or separated. Here atoms are neither destroyed nor reformed. In principle, no atom of an element is changed to that of another element. The situation is different in the nuclear fission, more about that later. A compound such as CO2 is composed of one carbon atom and two oxygen atoms, 1C and 2O. During a reaction the total mass does not change 1C + 2 O = 1CO2.
Examples:
The most known salt used for cooking is sodium cloride, NaCl. This compound consists of the two elements sodium, Na and chloride, Cl. You’ll find These two elements on the periodic systen,
Have a look on the periodic system! Na (on the very left) its atomic number is 11. Cl is on the same row (second last column on the left) atomic number 17.
The element of sodium Na has a nucleus of 11 protons, 12 neutrons and ist surrounded by a cloud of 11 electrons. So it’s an isotop: The number of protons and neutrons are not the same.
Chloride, Cl Atomic Nr 17: is it an isotop? yes, Number of Protons and neutrons is 35 and 37. there are two isotops of this element.
And Carbon, C Atomic Nr 6? There are two: the one with the same numbers of protons and neutrons = 12, this is an Atom, because as much protons like Neutrons.
The second one of nucleus C however has 7 neutrons and 6 Protons, it is an isotop. Those relative frequency is very low.