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Structure of the Atom Atomic number = number of protons in the nucleus and, in a neutral (+ = -) atom, the number of electrons outside it Atomic mass = total mass of protons + neutrons. It is always a whole number. Atomic mass – Atomic number = (protons + neutrons) – (protons) = number of neutrons

How many of each “sub-atomic part” (p, n, e-) are in these atoms? Fluorine (F) Atomic number = 9 Atomic mass = 19 Copper (Cu) Atomic number = 29 Atomic mass = 64

How many of each “sub-atomic part” (p, n, e-) are in these atoms? Fluorine (F) Atomic number = 9 = 9 p (+) = 9 e-Atomic mass = 19 (p + n) Atomic number = 9 = 9 p 10 n

How many of each “sub-atomic part” (p, n, e-) are in these atoms? Copper (Cu) Atomic number = 29 = 29 p (+) = 29 e-Atomic mass = 64 (p + n) Atomic number = 29 = 29 p 35 n

Isotope Notation Mg Symbol Written form: Magnesium - 25 Isotope Notation shows the symbol of the element with the atomic mass and atomic number on the left, with the atomic mass above (superscript) and the atomic number below(subscript) . Atomic Mass 25 “Symbolic Form” Mg Symbol Atomic Number 12 Written form: Magnesium - 25

Atomic Structure using Isotope Notation Atomic Mass 25 Mg Symbol Atomic Number 12 Number of protons = Atomic Number = 12 Number of electrons = number of protons = 12 Number of neutrons = Atomic Mass (p + n) 25 – Atomic Number (p) – 12 = 13 n

Practice 17 17 17 17 18 20 = Protons = = Electrons = = Neutrons = 35 37 Cl Cl 17 17 = Protons = = Electrons = = Neutrons = 17 17 17 17 18 20 These are two different isotopes of Chlorine: Chlorine-35 and Chlorine-37 They have the same atomic number (same number of p) but different masses (different number of n)

Tl Tl 204 205 81 81 = Protons = = Electrons = = Neutrons = 81 81 81 81 204 205 Tl Tl 81 81 = Protons = = Electrons = = Neutrons = 81 81 81 81 123 124 These are two different isotopes of Thallium: Thallium -204 and Thallium -205 They have the same atomic number (same number of p) but different masses (different number of n)

Complete the following sentences: How Atoms Differ pg 3 Complete the following sentences:   The number of ___________ in an atom is referred to as its atomic number. The periodic table is arranged by increasing ______ ________. Atomic number is equal to the number of __________ in an atom. The number of _________ in an atom identifies it as an atom of a particular element. The number of __________ plus the number of protons is equal to the atomic mass of an element. protons atomic number protons protons neutrons

Use the figures below to answer the following questions: Osmium 76 Os 190.23 Niobium 41 Nb 92.906 76 6. What is the atomic number of osmium? __________________ 7. What is the chemical symbol for niobium? ________________ 8. What is the atomic mass of osmium? ____________________ 9. What units is the atomic mass reported in? _______________ 10. How many protons and electrons does an osmium atom have? A niobium atom? ___________ ___________ Nb 190.23 amu 41 76

Mg Ne 24 12 22 10 atomic mass atomic number Label the mass number and the atomic number on the following isotope notation: atomic mass 24 Mg 12 _______________ atomic number _______________ Write each isotope below in symbolic notation. Use the periodic table to determine the atomic number of each isotope. 13. Neon-22 22 Ne 10

Write each isotope below in symbolic notation. Use the periodic table to determine the atomic number of each isotope. Helium-4 Cesium-133 Uranium-234 17.Cesium-132 4 He 2 133 Cs 55 132 Cs 55 < Isotopes of the same element > 234 U 92