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The Nature of Matter. Section 2.1. Atoms. Atom—the basic unit of matter Atoms are made up of three parts 1. protons—positively charged particles (+) 2. neutrons—carry no charge (0) 3. electrons—negatively charged particles (-) Nucleus—contains both the proton and neutron
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The Nature of Matter Section 2.1
Atoms • Atom—the basic unit of matter • Atoms are made up of three parts 1. protons—positively charged particles (+) 2. neutrons—carry no charge (0) 3. electrons—negatively charged particles (-) • Nucleus—contains both the proton and neutron • Electrons are in constant motion in the space surrounding the nucleus • Atoms have equal numbers of protons and electrons
Elements and Isotopes • Element—pure substance that consists of one type of atom • Represented by a one- or two-letter symbol • Symbol for Oxygen=O • Atomic number for Oxygen is 8 • Atomic number is equal to the number of protons in the nucleus • The atomic number for an element will not change
Isotopes • Isotope—atoms of the same element that contain a different number of neutrons • Mass number—sum of the protons and neutrons in the nucleus of an atom
Chemical Compounds • Chemical compound—chemical combination of two or more elements in definite proportions. • Water contains two atoms of hydrogen for each atom of oxygen • Chemical formula is H2O • Physical and chemical properties of individual elements are different from those of the compound that they form • NaCl
Chemical Bonds • Atoms in compounds are held together by chemical bond • Bond formation involves the electrons that surround each atomic nucleus • Main types of chemical bonds are ionic bonds and covalent bonds
Ionic Bonds • Ionic bond is formed when one or more electrons are transferred from one atom to another • An atom that loses electrons has a positive charge • An atom that gains electrons has a negative charge • Ion—positively or negatively charged atoms
Covalent Bond • Covalent bond—forms when electrons are shared between atoms • Molecule—formed when atoms are joined together by covalent bonds • A molecule is the smallest unit of most compounds
Picture Credits • http://www.oralchelation.com/technical/images/atom2.jpg • http://images.google.com/imgres?imgurl=http://www.vtaide.com/png/images/atom.jpg • http://www.starsandseas.com/SAS_Images/SAS_chem_images/elehydrogen.gif • http://www.uwm.edu/Dept/EHSRM/RAD/Figure_1.jpg • http://library.thinkquest.org/04oct/01590/intro/h2o.jpg • http://i108.photobucket.com/albums/n7/chemnificent/reaction_intro_1_240.jpg • http://www.vias.org/feee/img/00257.png • http://lc.brooklyn.cuny.edu/smarttutor/core3_21/images/nature/9.a.Ionicbond-nacl.gif • http://upload.wikimedia.org/wikipedia/commons/thumb/1/19/Covalent_bond_hydrogen.svg/700px-Covalent_bond_hydrogen.svg.png • http://www.gcsescience.com/Methane-Molecule.gif