Structure of Atoms Notes
1) All matter is made up of tiny particles called atoms. Atoms are considered the smallest part of matter. These particles keep the same characteristics of what the matter has. All atoms are about the same size and they are VERY small. It would take up billions of atoms to make up the period at the end of this sentence.
2) The Electron Cloud model is the accepted model of an atom. All atoms have the same basic parts: nucleus, protons, neutrons, and electrons. The nucleus is the heavy, center of the atom and holds the protons and neutrons. The electrons constantly move around the nucleus. Protons, electrons, and neutrons are called subatomicparticles because they are smaller then the atom itself. However, protons, neutrons, and sometimes electrons cannot exist by themselves like an atom, so therefore they are not considered the smallest part of matter.
3) Protons exist in the nucleus of the atom. They have a positive electrical charge (+). Protons always stay the same number with in that specific atom or element and do not move out of the nucleus.
4) Neutrons also exist in the nucleus of an atom. They have a neutral electrical charge(0.) Neutrons also stay the same within the nucleus of an atom and do not move out of the nucleus.
5) Electrons are smaller than both protons and neutrons. Electrons have a negative electrical charge (-). They are constantly in motion OUTSIDE the nucleus. Electrons are capable of moving from one atom to another. Electrons move around the nucleus in shells or levels. Shells are the distance from the nucleus the electron spins. Most of the time each shell can only hold a specific number of electrons and K shell must fill first, then L shell fills, and them M shell fills. The first shell (K) holds only 2 electrons. The 2nd shell (L) holds 8 electrons, and the 3rd shell (M) holds up to 18.