Transcript Atom
How is the Periodic Table organized? HON-17 BrINClHOF Anytime these elements are not in a compound, they exist as a diatomic molecule H2, N2, O2, F2, Cl2, Br2, I2 Elements are arranged: Vertically into Groups Horizontally Into Periods Why? That is what you are going to investigate now!!! Periodic Table Explanation Elements Song What do you know about any element in Period 2 ? In Group 17? Periodic Trends Activity Periodic Table wkst If you looked at one atom of every element in a group you would see… Each atom has the same number of electrons in it’s outermost shell. [aka – valence electrons] • An example… The group 2 atoms all have 2 electrons in their outer shells Be (Beryllium) Atom Mg (Magnesium) Atom • The number of outer or “valence” electrons in an atom effects the way an atom bonds. • The way an atom bonds determines many properties of the element. • This is why elements within a group usually have similar properties. If you looked at an atom from each element in a period you would see… Each atom has the same number of energy levels An example… The period 4 atoms each have 4 electron containing shells 4th Shell K (Potassium) Kr (Krypton) Atom Atom Fe (Iron) Atom Each group has distinct properties • The Periodic Table is divided into several groups based on the properties of different atoms. What are 5 properties that are unique to metals? Do metals tend to form positive or negative ions? Alkali Metals Soft, silvery colored metals Very reactive!!! Alkaline Earth Metals Silvery-White Metals Fairly reactive Many are found in rocks in the earth’s crust Transition Metals Most are good Conductors of electricity Malleable (easily bent/hammered into wires or sheets) Metalloids lie on either side of these “stairsteps” They share properties with both metals and non-metals Si (Silicon) and Ge (Germanium) are very important “semi-conductors” Nonmetals Brittle Do not conduct electricity Halogens Most are Poisonous Fairly reactive Noble Gases Unreactive Gases at room temperature Jellyfish lamps made with noble gases artist- Eric Ehlenberger Lanthanide Series Actinide Series Alien Lab Which elements have the most similar chemical properties? K and Na K and Cl K and Ca K and S • size of atom • measured from center of nucleus to outside of electron cloud • Gets smaller across a period due to proton(nuclear) pull • Gets larger down a group due to extra energy levels Found on Reference Table S Is the energy necessary to remove one electron from a neutral atom Explaining the trend: •The size of the atom •Write the symbol of the element • Put one dot for each valence earound the symbol •There are 4 sides •Each side can hold 2 e- •• • Te • •• The following is the order for e- 1 2 5 8 X 7 4 3 6 Calcium Iodine Carbon Hydrogen •• •• Ca • •I• •• • • •C • • H For ions What happens when an atom forms a positive ion? Loses electrons And becomes smaller What happens when an atom forms a negative ion? Gains electrons And becomes LARGER Magnesium ion Fluoride ion Oxide ion Potassium ion Mg +2 •• -2 ••O •• •• • • •• •• F •• K -1 + What is the most reactive nonmetal? What is the name of the element in Group 9, Period 6? Electronegativity is the ability of an atom to steal an electron from another atom Explaining the trend: •Number of protons in the nucleus • The distance from the nucleus • Different forms of the same element, due to bonding differences • Only certain elements in groups 13-16 Results in different chemical and physical properties Example - Oxygen O2 - oxygen Graphite Diamond Buckminsterfullerene Which atom of the following pairs of atoms have the greatest electronegativity? (Just use your HDCRT) K or Ge N or Sb Which element forms an ion that is larger than its atom? 1) +2 Ca 2) +3 Al 3) Cl 4) + H Halogen Lab Use R.T. to determine if an element is a solid, liquid, or gas under certain conditions. Gas F2 @ 100 K Cu @ 1400C Liquid K @ STP Solid An atom has 7 protons, 7 electrons, and 7 neutrons. Draw its dot diagram. Practice Exams Analysis by Separation Lab