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Chapter 17 Sec 1-4 Structure of the Atom Elements Any material made up of only one type of atom is classified as an element. Example – Pure gold contains only gold atoms Example – Nitrogen gas contains only nitrogen atoms All the elements are listed on a chart called the periodic table. Scientific Shortcuts! Do you have a nickname? What about abbreviations for the names of states or classes? EX: PS – Physical Science IL – Illinois Scientists do this too – especially in CHEMISTRY! Chemistry Shortcuts! Elements are abbreviated with certain atomic symbols. Many of these symbols come from Latin roots. Elements are named after people, places, or properties. EX: H for Hydrogen He for Helium O for Oxygen Fe for Iron Hydrogen Hydrogen was the first element to exist in the universe. It is the most common element – makes up more than 90% of all atoms. Hydrogen is very light and has a simple structure. Size of an Atom Atoms are so small they can’t be seen with visible light. We could stack microscope upon microscope and never be able to “see” an atom. Photographs of atoms are obtained with a scanning tunneling microscope. This is a non-light imaging device that bypasses light and optics. Atomic Components Remember Your Charges!! Protons and Neutrons are found in the nucleus of the atom Nucleus is the positive center of the atom Electrons are circling around the outside of the nucleus. Atomic Nucleus The atomic nucleus contains protons and neutrons. It makes up most of the mass of the atom, even though it is extremely small. Electrons move around the nucleus. Most of the rest of the atom is empty space. Parts of the Atom Subatomic Particle Mass Compared to an Electron Particle Charge Symbol Location Proton +1 p+ 1836 Nucleus Neutron 0 n0 1841 Nucleus Electron -1 e- 1 Electron Cloud Let’s get on with the Chemistry! ATOMIC NUMBER=# of protons in nucleus of atom Always whole numbers! Each atomic number is unique to a particular element! Ex: All atoms with the atomic number 8 are oxygen atoms, all oxygen atoms have the atomic number 8! Mass Number MASS NUMBER = total # of particles in the nucleus MASS NUMBER = total number of protons and neutrons Ex: Boron has mass number of 11 and atomic number of 5. So it has 5 protons and 6 neutrons. Isotopes ISOTOPES=atoms of the same element with different numbers of neutrons. A majority of elements exist as isotopes. Ex: Helium 4 Neutrons 5 Neutrons Isotope Symbols Mass Number Atomic Number 56 Fe 26 Atomic Symbol • The superscript is the atomic mass. • The subscript is the atomic number. Atomic Mass The total mass of an atom is the atomic mass. This is an average mass! It’s the average mass of all its various isotopes! This is the mass shown on the periodic table. Elements have different masses! ATOMIC NUMBER ATOMIC MASS And they all lived happily ever after in Chemistryland!