Transcript Atom Notes
TEKS 8.5A describe the structure of atoms including the masses, electrical charges and locations, of protons and neutrons in the nucleus and electrons in the electron cloud TEKS 8.5B identify that protons determine an element’s identity and valence electrons determine its chemical properties, including reactivity Exploring Inner Space All matter is made up of atoms. All atoms are made up of Protons Neutrons Electrons Each particle has specific properties, such as location, electric charge and mass. All atoms of the same element have same number of protons. The number of protons determines the element’s identity. atomic number = # of Protons. Structure of the Atom The Nucleus The center of the atom is called the nucleus . 3 Li 6.941 Lithium proton nucleus neutron The nucleus contains protons and neutrons. The nucleus makes up the mass of an atom. Atomic Mass = # Protons + # Neutrons Proton = 1 atomic mass unit (amu) Neutron = 1 atomic mass unit (amu) If Lithium has 3 protons and 4 nuetrons, what is the atomic mass of the atom? 7 The Periodic Table shows the atomic mass for each element as a decimal. Round the atomic mass to find the number of protons or neutrons. If the mass number is known, and you know the number of protons, how can you find the number of neutrons? # Neutrons = Mass # - # Protons The Electron Cloud and Energy Levels Surrounding the nucleus is the electron cloud. Electrons orbit around the nucleus in different energy shells (levels). energy levels Electrons are so small that they are NOT included in the atomic mass. Energy levels can only hold a certain number of electrons in each energy level. The first energy level holds up to 2 electrons. The second energy level holds up to 8 electrons. The third energy level may hold 8 or more electrons. first energy level second energy level third energy level 8 or more! How many electrons are in each energy level of the element Lithium? st nd 1 – 2, 2 – 1 electron cloud 3 electron Li energy levels 6.941 Lithium Valence Electrons Valence electrons are the # of electrons in the outer most energy level. Valence electrons….. valence electrons are found here! Valence electrons determine how reactive it is with other elements. Charges on particles Protons = positive charge. Electrons = negative charge. Neutrons = have no charge. A stable atom has the same number of protons and electrons. 8 Protons + + + + + + + + = 8 Electron - The positive and negative charges cancel out and there is no charge. EXIT TICKET Particle Proton Neutron Electron Charge Mass Location