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ATOMS and PERIODIC TABLE Pg. 54 The Structure of Atoms Atomic Theory – states that all matter is made up of tiny particles called atoms. Matter is defined as anything that has mass and takes up space. Pg. 54 The Structure of Atoms Atoms are made up of three subatomic particles: Protons – positive charge Neutrons – no charge; neutral Electrons – negative charge Protons, quarks. Protons Neutrons, and Electrons are made up of particles called and Neutrons are located in the nucleus of an atom Electrons are located outside the nucleus in random patterns, but clustered in electron shells. Pg. 54 The Structure of Atoms Electron The Shells first electron shell has no more than two electrons. The Second shell can have as many as eight electrons. The other shells have varying numbers of electrons depending on the number of electrons in the atom. The last electron shell usually will hold no more than eight electrons. Pg. 56 Properties of Elements In the Periodic Table The number of protons in an atom gives the atom its identity. Atoms that have the same number of protons are called elements. Elements are arranged according to their atomic number on the periodic table. The atomic number corresponds to the number of protons or electrons in the atom. Pg. 56 Properties of Elements in the Periodic Table The atomic mass is the number of protons plus the number of neutrons found in the atom. Electrons do not contribute to the mass of the atom because they are so small. Protons + Neutrons = Atomic Mass Pg. 56 Properties of Elements in the Periodic Table Atoms of the same element do not always have the same number of neutrons. Atoms that have different numbers of neutrons are called isotopes. The atomic mass given on the periodic table is the average of all the isotopes and is not a whole number. To find the number of neutrons for an element, subtract the number of protons (atomic number) from the atomic mass. Atomic Mass – Atomic Number = Number of Neutrons Pg. 56 Properties of Elements in the Periodic Table The periodic table is made up of elements placed in organized rows and columns according to properties and size. Rows are called period and are arranged according to the atomic numbers. Columns are called families and have similar properties and always have the same number of electrons in their outer shell. You can remember that families of people have similar characteristics or properties and a family tree goes down. Pg. 57 Properties of Elements in the Periodic Table Elements can all be classified as metals, nonmetals, metalloids, or noble gases. Metals: Make up the majority of the table and are located to the left. Hydrogen Are is the only exception. solids at room temperature, are hard, have luster (shiny), and conduct heat and electricity. Pg. 57 Properties of Elements in the Period Table Nonmetals: Right side of the periodic table. Usually gases or dull, brittle solids at room temperature. Metalloids: Elements diagonally between the metals and nonmetals. Have properties of both metals and nonmetals. Used in semiconductors and computer chips. Pg. 57 Properties of Elements in the Periodic Table Noble Gases: Located in one family; Family VIIIA Far right column of the periodic table Nonmetal gases that do not react with any other elements. Pg. 61 Reactivity of Elements in the Periodic Table An element is most stable when its last electron shell is full. All elements have outer shells that can hold 8 electrons. Exception: Hydrogen and Helium Pg. 61 Family VIIIA Noble gases have 8 electrons in their outer shells Exception: 2 electrons. Very Helium, but is complete with only stable elements Will not react with other elements Pg. 61 Family IA Alkali Metals Exception Very is Hydrogen (non metal) reactive Have only one electron in the outer shell Give up its one electron forming ions Pg. 61 Family IIA Alkaline Have Earth Metals 2 electrons out of 8 possible in their outer shell Very reactive, but less reactive than the Alkali Metals Pg. 62 Family B Transition Metals found in the middle of the periodic table. Reactivity of these metals increases as you go down the periodic table and from right to left. Pg. 62 Family VIIA Halogens Most reactive nonmetals Have 7 out of 8 possible electrons in their outer shell Combine with metals to form a salt Example: Na + Cl → NaCl Pg. 62 Family VIA No common name Have 6 of 8 possible electrons in their outer shell Not as reactive as the halogens Pg. 62 Family IIIA through VA No common name Family IVA is half full making it more stable than IIIA or VA on either side of it. Pg. 64 Bonding of Atoms Atoms of different elements combine chemically to form compounds Done by sharing or transferring electrons Electrons in the outer shell of an atom are called valence electrons Ionic bonds result in the transfer of electrons from atom to atom. Pg. 64-65 Bonding of Atoms Ionic bonds are usually present in compounds which have metal atoms bonded with nonmetal atoms Covalent bonds are when two or more atoms share electrons Usually present with two or more nonmetals Pg. 69 Radioactivity Atoms of the same element can have different numbers of neutrons. Atoms of the same element that have different numbers of neutrons are called isotopes When there are too many neutrons in the nucleus the nucleus becomes unstable. An unstable isotope will be radioactive and is called a radioactive isotope Pg. 69 Radioactivity Radioactive particles: Alpha 2n atoms give off three Particles – helium nucleus with 2p and When an alpha particle is given off the atomic number of the parent nucleus is reduced by two If ingested will do more damage to internal tissues than other forms of radiation. Pg. 70 Radioactivity Beta Particles – electrons emitted Penetrate more than alpha particles but can be stopped by lead Gamma Can All Particles – high energy x-rays only be stopped by thick lead or concrete elements with atomic numbers greater than 83 are radioactive Pg. 70 Radioactivity A radioactive atom that emits an alpha, beta, or gamma particles is going through a process called radioactive decay Radioactive decay causes an atom of one element to become a different element by reducing its atomic number The half-life of a radioactive atom is the time it takes for ½ of the particles in the nucleus to decay Pg. 71 Fission Fission occurs when the nucleus of an atom that is so unstable that it splits into two smaller atoms. Releases a large amount of energy Used in nuclear reactors Reactors use control rods to absorb excess energy Nuclear bombs have no control rods and release all of the energy in one blast Pg. 72 Fusion Fusion is when two small atoms are joined together to form a larger atom Produces energy also Requires high temperatures Occurs in the sun when two hydrogen atoms fuse to form a helium atom Scientists are still working to recreate this but can’t generate the high temp Pg. Pg. Pg. Pg.