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Atomic Structure Chapter 4.1 Pages 70-76 Atomic Theory Every element is made of tiny, unique particles called atoms that cannot be subdivided. Atoms of the same element are exactly alike. Atoms of different elements can join to form molecules. Parts of the Atom Nucleus Dense center of the atom Subatomic particles Proton Neutron Electron Proton Has a +1 charge Mass of 1.67 x 10-27 kg Located inside the nucleus Neutron Has no charge Mass of 1.67 x 10-27 kg Located inside the nucleus Electron Has a negative charge Mass of 9.11 x 10-31 kg Moving around outside the nucleus. Charge of an Atom Atoms are neutral The positive protons and negative electrons cancel each other out. Nucleus has a positive charge because it contains protons. How do we know find out about the atom Everything we need to find out about the subatomic particles in the atom is on the Periodic Table How do we know the number of subatomic particles in an atom? Atomic number: this number indicates the number of protons in an atom The atomic # for any given element NEVER changes Ex: Hydrogen’s atomic number is 1 So hydrogen has 1 proton Ex: Carbon’s atomic number is 6 So carbon has 6 protons **The number of protons identifies the atom. Ex. 2 protons = ?, 29 protons = ? Atomic Number on the Periodic Table Atomic Number Symbol 11 Na LecturePLUS Timberlake 10 How do we know the number of subatomic particles in an atom? Mass number: the number of protons and neutrons in the nucleus Protons + Neutrons = Mass Number Ex: Find the mass of Lithium (Li) Atomic Mass Determining the number of protons and neutrons Li has a mass number of 7 and an atomic number of 3 Protons = 3 (same as atomic #) Mass # - Atomic # = Neutrons Neutrons= 7-3 = 4 Ne has a mass number of 20 and an atomic number of 10 Protons = 10 Neutrons = 20 - 10= 10 Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35Cl 37Cl 17 17 chlorine - 35 chlorine - 37 LecturePLUS Timberlake 14 ions If protons ≠ electrons the atom is called an “ion” Protons -- Electrons Charge of the atom If protons > electrons : positive charge If protons < electrons : negative charge Energy Levels Electrons can be located in a specific energy level Gain energy to move to a higher energy level. Lose energy to move to a lower energy level. Energy Levels 1st Level – contains 2 e 2nd Level – contains 8 e 3rd Level – contains 18 e 4th Level – contains 32 e 5th to 7th Level – contains 32 e- each Sublevels 1st level has 1 sublevel 2nd level has 2 sublevels 3rd level has 3 sublevels 4th level has 4 sublevels Orbitals s orbital – holds 2 e p orbital – holds 6 e d orbital – holds 10 e f orbital – holds 14 e s orbital Can hold a maximum of 2 electrons p orbital Each p orbital can hold 2 electrons. All three can hold a maximum of 6 electrons.