Atomic Structure
Chemistry Joke Q: Where does a German chemist put his dirty dishes? A: In the Zn!
Modern View The atom is mostly empty space with 2 regions: Nucleus with protons and neutrons Electron cloud— region where you are most likely to find an electron
3 Subatomic Particles Electrons – negative charge Protons – positive charge Neutrons – neutral (no charge) - - - + + + + - - Protons and neutrons are made up of even smaller particles called quarks. *VIDEO*
How Many Protons? Each atom has a unique number of protons that will NEVER change. ATOMIC NUMBER: The number of protons in the nucleus of an atom Ex. All atoms of oxygen have 8 protons, so the atomic number of oxygen is 8. The atomic number (the number of protons) identifies the element.
Atomic Number on the Periodic Table 11 Na Atomic Number 11 Protons Symbol
How many protons does each atom have? Nitrogen Sulfur Barium 7 16 56
How Many Electrons? An atom is neutral. The net charge is zero. If every element has positive protons in its nucleus then why don’t elements have a positive charge? Because…the number of electrons equals the number of protons in a neutral atom. The charges cancel. The net charge is zero.
Ions Atoms can gain or lose electrons. When this happens, the atom becomes charged and we call it an ION. If an atom loses electrons, it becomes positively charged. If an atom gains electrons, it becomes negatively charged. 9
How Many Neutrons? Atoms of the same element always have the same number of protons, but they can have different numbers of neutrons! We call atoms of the same element that have a different # of neutrons ISOTOPES.
Isotopes To identify isotopes, we have to use a mass number. The MASS NUMBER is the total number of p+ and no added together. p+ + no = mass number Therefore…mass # ─ # p+ (atomic #) = # no Ex. One carbon isotope has 7 neutrons. All carbon atoms have 6 protons, so its mass number is 13. Written as a name: Carbon-14 14 Or as a symbol: C 6
Isotopes The mass number is NOT given on the periodic table!!!! The number on the periodic table is the ATOMIC MASS. That number is the weighted average mass of all of the isotopes of that element. Atomic Mass has decimal places. The Mass Number ( protons + neutrons) will always be a WHOLE Number. 12
Finding the # of Neutrons Ex. Beryllium-9 atomic # 4 mass # 9 # neutrons = 9 - 4 = 5 neutrons HOW MANY PROTONS? ____ ELECTRONS?___ 4 4
Subatomic Particles in Oxygen, Phosphorus, & Zinc Mass # 16 31 65 O P Zn 8 15 30 __ p+ __ p+ __ p+ __ n __ n __ n __e- __e- __ e- Atomic #
Chemistry Joke Q: What do you do with a dead chemist? A: Ba!