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Mass Number Isotopes Ion Sub atomic Particles: particles inside an atom Proton = p+ Electron = e Neutron = n0 Protons & Neutrons have the most mass and are located in the center of the atom – nucleus. Electrons are have such a small mass – they are considered almost massless Atomic # is the number at the top of each block on the periodic table Atomic # = #p Neutral Atom #p = #e- 1 H 1.00784 Number of protons and neutrons in the nucleus always a whole number NOT on the © Addison-Wesley Publishing Company, Inc. Periodic Table! mass # = protons + neutrons Hyphen Notation: element name – mass # Nuclear Symbol: Mass #atomic #symbol Hyphen notation: carbon-12 Nuclear symbol: Mass # Atomic # 12 6 C Chlorine-37 › atomic #: 17 › mass #: 37 › # of protons: 17 › # of electrons: 17 › # of neutrons: 20 37 17 Cl Carbon – 12 Atomic # Mass# #P #E #N What is the same? What is different? Carbon – 14 Atomic # Mass# #P #E #N Atoms of the same element with different mass numbers.(because of different #neutrons) © Addison-Wesley Publishing Company, Inc. Boron – 10 Boron – 11 Boron – 13 Which of these has more neutrons? There are billions and billions of atoms in any element on the periodic table. All the atoms in element have isotopes: same atom but with a different mass. How do we know what the mass of all those atoms will be? 12 12 148 12 12 12 12 12 12 14 8 12 Average Atomic Mass Average Atomic mass: the average mass of ALL the isotopes of that element. This number is located on the bottom of each block on the periodic table Not a whole number Different from the Mass # Mass #: is the mass of a single atom Similar to a grade on an assignment in class. Average Atomic Mass: is the average mass of billions of atoms Similar to your average at the end of the year – an average of all your assignment grades 12 12 148 12 12 12 12 12 12 14 8 12 Average Atomic Mass Models: reasonable representation of a very large or a very small object. Atoms are very tiny and we can not physically see the parts of an atom – so a model (drawing) is used to represent the atom. Atomic structure is an important property of an atom and it must be represented correctly. Proton & Neutrons are in the nucleus, Electrons move around the nucleus – but they are in specific locations around the nucleus. Electrons are very tiny, have almost no mass, and move very fast. The location of an electron is hard to identify because it moves so fast – so electrons are modeled by an electron cloud or ring around the nucleus. When drawing models of atoms – it is important that the electrons are drawn in the correct ring! The most important electrons in an atom are the valence electrons. Valence electrons are the electrons in the last ring. › Determine the ion charge › Determine the chemical properties › Determine the type of bonding Drawing of an atom that includes the 3 sub atomic particles. (drawing of the PEN table) Protons and neutrons in nucleus Electrons in rings around the nucleus › 2 electrons in 1st ring › 8 electrons in 2nd ring Boron – 11 Atomic # Mass# #P #E #N # Valence electrons Draw a Bohr Model for the following: Beryllium – 7 P E N Magnesium – 24 P E N # Valence electrons