# Warm-Up (10/1/14) 1.Write the charge and symbol for a proton, neutron, and electron. 2.If an atom has 37 protons, how many electrons must it have? Why?

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Warm-Up (10/1/14) 1.Write the charge and symbol for a proton, neutron, and electron. 2.If an atom has 37 protons, how many electrons must it have? Why? Pass forward your Rutherford Newspaper Article. Make sure the Rubric is stapled to the top.

Ch. 4 Notes (cont.) How Atoms Differ

I.Properties of Subatomic Particles ParticleSymbolLocationRelative Charge Relative mass Actual mass (g) Electron e - or In the space surrounding the nucleus 1- _1__ 1840 9.11 x 10 -28 Proton p+ or In the nucleus 1+1 1.673 x 10 -24 Neutron n 0 or In the nucleus 01 1.675 x 10 -24

II. Atomic Number the number of protons in an atom Identifies element – each atom has unique # – # never changes Periodic table is arranged in increasing atomic #

III. Mass Number represents the total number of protons and neutrons in the nucleus # of neutrons = mass number – atomic number Rounded atomic mass number Ex: What is the mass number for boron? ANS: 11 (Round 10.81 up to 11) Ex: How many neutrons does boron have? ANS: 6 neutrons (11-5 = 6)

IV. Isotopes Atoms of the same element but have a different # of neutrons Ex: 3 isotopes of carbon

All elements have isotopes (some 2, some 3, etc.) Some isotopes are naturally radioactive. Ex: Plutonium

V. Representing Isotopes In Ag-107, the 107 represents the mass number (neutrons + protons) OR:

Practice: 1. What is the mass number for Co-59? 2. What is the mass number for 59 7

VI. Atomic Mass The standard is the atomic mass unit (amu): defined as 1/12 of the mass of a carbon-12 atom the weighted average of the isotopes of that element. Formula: Atomic mass of an element = ( % abundance of Isotope #1 x mass of Isotope #1 ) + ( % abundance of Isotope #2 x mass of Isotope #2 ) + …

Practice 3 Silver has two naturally occurring isotopes. Ag-107 has an abundance of 51.82% and mass of 106.9 amu. Ag-109 has a relative abundance of 48.18% and a mass of 108.9 amu. Calculate the atomic mass of silver.

Practice 4 Rubidium is a soft, silvery-white metal that has two common isotopes, Rb and Rb. If the abundance of 85 Rb is 72.2% and the abundance of 87 Rb is 27.8%, what is the average atomic mass of rubidium? 85 37 87 37

Vocabulary to Know Atomic #: # of protons Mass #: # protons + # neutrons written 2 ways: Carbon-14 or C Isotopes-same # of protons, different # of neutrons Atomic mass-weighted average mass 14 6

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