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Concept Summary Batesville High School Science Atoms Atoms are the building blocks of matter. Anything that takes up space is made of atoms. Kinds of Atoms There are about 110 different kinds of atoms. About 90 kinds of atoms occur naturally. About 20 kinds of atoms occur only in the laboratory. Elements Each kind of atom is called an element. Each element has a name and a symbol. Kinds of Atoms About 90% of the atoms in the universe are the lightest element, hydrogen, (H). Most of the rest of the atoms in the universe are the next lightest element, helium (He). The 88 other natural elements are relatively rare in the universe. Your Atoms Living things are made mostly of: Carbon (C) Oxygen (O) Hydrogen (H) Nitrogen (N) Calcium (Ca) The Atmosphere The Earth’s atmosphere is about 80% nitrogen (N). Most of the rest of the atmosphere is oxygen (O) Atoms Are Recyclable Atoms are almost indestructible. The atoms in your body were once part of other matter. When you die, your atoms are not destroyed - they become part of something else. Atoms can combine and recombine with other atoms. Atoms are Recyclable Atoms heavier that helium (He) were probably made in intense stellar explosions called supernova. Elements can be converted to other elements by radioactive processes. Atoms are Small gram of water contains about 1023 atoms (100,000,000,000,000,000,000,000) There are more atoms in your lungs right now than there are breathfulls of air in the atmosphere. Atoms cannot be seen - even with the most powerful microscope. 1 Atoms Move All atoms are in constant motion. In solids, atoms mostly vibrate in place. In liquids, atoms are somewhat free to move about. In gasses, atoms are almost completely free to move about. Evidence for Atoms motion - “jiggling” of microscopic pollen grains in water Brownian Discovered in 1827 by Robert Brown Explained in 1905 by Albert Einstein Electron Microscope (1970s) Scanning Tunneling Electron Microscope (1980s) Molecules Atoms can combine to form molecules. Molecules can contain from two to many thousands of atoms. Two oxygen atoms like to combine to form an oxygen molecule (O2) Water is made of two hydrogen atoms and one oxygen atom (H2O) DNA is a huge, helix-shaped molecule. Compounds Molecules composed of atoms of different types are called compounds. Water (H2O) Carbon dioxide (CO2) Salt (NaCl) The combination of symbols H2O is a chemical formula. The Atomic Nucleus Almost all of the mass of an atom is concentrated in a tiny central region called the nucleus. Discovered in 1911 by Ernest Rutherford The nucleus is less than a trillionth of the volume of an atom. What’s in a Nucleus? The nucleus has 2 primary building blocks: Protons - positive electric charge Neutrons - electrically neutral Protons and neutrons have approximately the same mass Protons and neutrons are called nucleons. Atomic Number The number of protons in an atom’s nucleus determines the type of atom (element) it is. 1 proton = hydrogen 2 protons = helium 6 protons = carbon 8 protons = oxygen The number of protons in an atom is the atomic number of the atom. Isotopes An isotope of an element has the same number of protons, but a different number of neutrons. Helium = 2 protons + 2 neutrons Isotope of Helium = 2 protons + 1 neutron The Rest of the Atom Outside the nucleus, the atom is almost completely empty. Electrons (negative charge) orbit the nucleus. Electrons have about 1/2000 the mass of protons and neutrons. Electrons & Ions Normal atoms have the same number of electrons and protons. Electrons are arranged in “shells” in the atom. An ion is an atom with too many electrons (negative ion) or too few electrons (positive ion) The Periodic Table The Periodic Table of the Elements lists atoms by atomic number and electron arrangement. Element to the right has one more proton Element below has one more electron shell Elements in a column are a group - they have similar chemical characteristics. Phases of Matter Solid Liquid Atoms are free to slide over other atoms Gas Atoms held in place by other atoms Atoms can vibrate in place. Atoms are completely free to move about. Plasma Positive ions and free electrons No complete atoms Most common form in the universe The End
