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Matter and Periodic Table Matter- anything that has mass and takes up space 2 Categories: 1. Pure Substance- fixed composition A. Elements- all atoms of a substance have the same identity * ~92 in nature * 20 + synthetic *Elements are represented with a chemical symbol Ex: oxygen = O B. Compounds- 2 or more elements combine in a fixed portion *represented with a chemical formula *Ex: H2O 2. Mixtures- 2 or more substances A. Heterogeneous- different substances can be distinguished Ex: taco, garden salad and cereal B. Homogeneous- 2 or more gases, liquids or solids blended evenly Ex: Sugar water, Kool Aid All matter is made up of Atoms Atoms * smallest particle of matter that contain the characteristics of an element. Nucleus-center of the atom; contains protons and neutrons A. Proton - positive charge - Identifies the atom - Atomic # = # of protons B. Neutron- no charge - Mass atom = protons + neutrons Electrons are located in the electron cloud. Electrons- negative charge - Responsible for all bonding - Found on energy levels - Mass is so small it isn’t included in the mass number Example: atomic number = 57 and mass = 139 Protons= Neutrons= Electrons= 17 protons and 18 neutrons Electrons= Mass= Atomic Number = -If two atoms of the same element have different number of neutrons then it is an isotope. Atomic Mass = found on the periodic table = average of all isotopes masses Changes the mass number but the atomic number remains the same. Ex: Carbon-14 Carbon -12 Mass = 14 Mass = 12 Protons = 6 Protons = 6 Neutrons = 14-6 Neutrons = 12-6 =8 =6 Periodic Table *a method of displaying the chemical elements How many natural elements exist? How many synthetic elements exist? *Scientist create new nuclei to make new elements. Organization of the Periodic Table Groups or Families: - Columns of the periodic table - Radius increases as you move down the PT - Have similar properties because of the same # of valence electrons Period: - Rows of the periodic table - Each period represents a new energy level Metals: - Atoms lose electrons to form positive ions - Located to the left of the metalloids - Largest portion of the periodic table - Good conductors Nonmetals: - Atoms that gain electrons for form negative ions - Located to the right of the metalloids - Bad conductors Metalloids: - A blend of metals and nonmetals - Referred to as the staircase - Displays characteristics of metals and nonmetals 92 U Uranium 238 ProtonsNeutronsElectronsMass Isotopes- 2 atoms of the same element that have different # of neutrons but the same number of electrons Helium-3 Helium- 4 Carbon-13 Carbon-14 Density Density = Mass / Volume cm3 or kg/L Units: g/mL, g/ *Density is the same for a substance no matter how much you have. Example: 50g Copper Density = 8.92 g/ml 100 g Copper Density = ________________ *Density can be used to identify a pure substance. Example : Density of gold = 19.31 g/ml You can use this information to test a piece of jewelry to see if it is real or not! Density of water = 1 g/ml *If something is more dense than water it will ______________. *If something is less dense than water it will _______________. Why does the egg float is the salt water (left) but sink in the pure water? Water Displacement- The movement of water upward when an object is place in a container containing water. Ex: **What would be formed if a large section of an iceberg broke off and landed in the ocean?