1. The Atom Chapter 4.2

2. Atoms: Are the smallest unit of an element that maintains the properties of that element. All atoms have a diameter of 0.0000003 CM = 3 one hundred millionth of a cm. Even things that are very thin like aluminum foil are made up of large numbers of atoms.

3. Atoms are made up of even smaller particles Electrons, neutrons, protons and (nucleus). Protons & Neutrons are about the same size. It takes about 2,000 electrons to equal the mass of 1 proton. Protons and Neutrons are found in nucleus. Electrons are found just outside in the nucleus. (Know for your model)

4. Protons: are positive & charged particles. Mass is extremely small, 1 AMU. Neutrons: are no charge or neutral. Has more mass than protons but still has mass of 1 AMU. P/N located inside the nucleus Electrons: located outside the nucleus in electron clouds. Negative charged. Particles of an atom very small.

5. Electrons: is a negative charged sub-atomic particle that is just outside the nucleus. Electrons are smaller than protons and neutrons. It takes 1,800 electrons to equal the mass of 1 proton The charges of protons and electrons are opposite but equal, so their charges cancel out. If it protons and electrons are not of equal numbers and the atom becomes a charged particle called an ion.

6. An atom that loses an electron becomes a positive charged ion. An atom that gains one or more extra electrons becomes a negative charged ion. Protons, neutrons, and electrons can be classified by mass, charge, and location in an atom.

7. Isotopes are atoms that have the same number of protons but have a different number of neutrons. Isotopes thus have a different atomic mass. There are around 280 stable isotopes of the natural elements. There are over 1800 artificial radio-isotopes produced by using numerous nuclear bombardment methods.

8. Over 110 different elements This means over 110 different Atoms. How are they different? By the number of P.E.N. Helium: 2 P’s 2 E’s 2 N’s Gold: 79 P’s 79 E’s 118 N’s Carbon: 6 P’s 6 E’s 6 N’s Atomic Number is the number of proton of that elements

9. Every Atom of a given element has the same number of protons and electrons. Atoms do not have the same number of neutrons. Isotopes are atoms of the same element that have different numbers of neutrons and different mass numbers. Same atomic number, different mass number because of different number of neutrons. Hydrogen has different physical and chemical properties in their isotopes.

10. Atomic number are on all elements of our periodic table. This atomic number of an element equals the number of protons and electrons in an atom. Many scientists refer to the atomic number of an element instead of referring to the name of or symbol of the element.

11. Periodic table also shows the mass number. This helps determine the number of neutrons in an atom. Mass number of an atom is the total of the protons and neutrons in the nucleus. You fin d the atomic number Au Gold 19 subtract the mass no. and you have the number of the neutrons in the atom or 117.97 Neutrons in Au

12. Atomic Mass Unit(AMU): Mass of an atom’s particles. Proton/Neutron = 1 AMU Electron = 1/836 AMU Atomic Number: Total Number of protons Mass number: Sum total of protons and neutrons in an atom. Atomic Mass: Weighted Average of the mass of isotopes of the sample element.