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Transcript
Chapter 17 Properties of Atoms and the Periodic Table Structure of the Atom Elements are abbreviated in scientific shorthand- first letter or two of an element’s name. Structure of the Atom- Cont. Atom- smallest piece of matter that still has the properties of the element. Protons have electrical charge of +1. Neutrons do not have an electrical charge. Electrons have electrical charge of -1. Protons and neutrons are in the nucleus of an atoms; electrons surround the nucleus. electron neutron proton Structure of the Atom- Cont. Protons and neutrons are made up of smaller particles called quarks. Six quarks are known to exist; the sixth is called the top quark. Structure of the Atom- Cont. Scientists used scaled-up models to represent atoms. Early models of atoms used a solid sphere. These are the actual wood spheres that Dalton used as models for atoms. They are about 200 years old. Notice the holes drilled in them. He probably used them to connect atoms to other atoms to make compounds. Structure of the Atom- Cont. Current electron cloud model shows electrons traveling in specific energy levels around a nucleus of protons and neutrons. Masses of Atoms Atomic Mass- composed mostly of the protons and neutrons in the nucleus. Unit of measurement of atomic particles is atomic mass unit. Atomic Number- the number of protons in an atom; number of protons also identifies the element. The sum of the number of protons and neutrons in the nucleus of an atom is the mass number. Masses of Atoms- Cont. Element Element Atomic Number Symbol Mass Number Masses of Atoms- Cont. Isotopes- atoms of the same element with different numbers of neutrons. Different isotopes have different properties. Number of neutrons is equal to the mass number minus atomic number. Masses of Atoms- Cont. Masses of Atoms- Cont. Name of element followed by mass number identifies the isotopes. Masses of Atoms- Cont. Average atomic mass is the weighted-average mass of an element’s isotopes. Average atomic mass is the closest to its most abundant isotope. The Periodic Table Elements are organized in the periodic table by increasing atomic number. The Periodic Table- Cont. In the late 1800’s, Dmitri Mendeleev derived the first periodic table based on atomic mass. The Periodic Table- Cont. The Periodic Table- Cont. In 1913, Henry G. J. Moseley arranged the elements by atomic number rather than atomic mass. The Periodic Table- Cont. Vertical columns in the periodic table are groups of elements with similar properties. Elements with the same group have the same number of electrons in their outer energy level. Each of the seven energy levels can have a maximum number of electrons. Energy level one can contain at most two electrons. Energy level two can contain at most eight electrons. The Periodic Table- Cont. The Periodic Table- Cont. Each row in the periodic table ends when an outer energy level is filled. The Periodic Table- Cont. Electron dot diagrams use the elements symbol and dots to represent outer energy level electrons. The Periodic Table- Cont. Periods- horizontal row of elements that contain increasing numbers of protons and electrons. Elements are classified as metals, nonmetals, or metalloids (semimetals). Elements are synthesized in laboratories all over the world. The Periodic Table- Cont. The Periodic Table- Cont. The same elements exist all over the universe. Hydrogen and helium are the building blocks of other naturally occurring elements. Supernovas spread heavier elements throughout the universe.