Do Now: (5 min) An atom of silver (Ag) has 47 protons and 54 neutrons. 1. What is the mass number? 2. How many charged particles does it have? Don’t forget to have your Do Now checked by Ms. Akagi to get full credit before time is up!

Do Now Discussion An atom of silver (Ag) has 47 protons and 54 neutrons. 1. What is the mass number? mass number = protons + neutrons = = How many charged particles does it have? charged particles = protons + electrons = 47 protons + 47 electrons = 94 charged particles

What Have We learned? (A LOT!) Gold Foil experiment: ◦ Atoms are mostly empty space (particles pass through the foil ◦ Atoms have a solid center called the nucleus (particles bounce off the foil) 3 subatomic particles: ◦ Protons ◦ Neutrons ◦ Electrons Atoms are neutral in charge Atomic number tells us element type Mass number = protons + neutrons # charged particles = protons + electrons

Isotopes and Elements 10/26/09 Agenda: 1. Cornell Notes 2. Exit Slip 3. Atom Brochures

Isotopes Atoms of the SAME element, but DIFFERENT numbers of neutrons ◦ Behave the same chemically, only affects stability ◦ Different mass numbers Writing Isotope Names: element – mass number (example: carbon-12) Example: How would we write the name of an atom with 6 protons and 7 neutrons? ◦ What element has 6 protons? ◦ What is the mass number? ◦ What is the name? Carbon 6+7 = 13 Carbon-13

Element Symbols Why do we use them? Shorthand notation – easier to write names of elements and compounds Standardization – all scientists use the same symbols (despite speaking different languages)

Element Symbol Rules 1. Each element symbol has 1 or 2 letters (Ag, K, O, etc) 2. The first letter is capitalized 3. In compounds, 2 or more symbols are placed together 4. Subscripts (little numbers) come after symbols and indicate how many atoms of each element are present MgSO 4

Examples: What elements are in the compound NaF? Sodium and Fluorine! What elements are in the compound MgBr 2 ? Magnesium and Bromine! How many bromine atoms are in MgBr 2 ? 2 atoms of Bromine!

Exit Slip Purpose: to see if we need to spend review time on these subjects for the test 5 short questions Answer all of them to the best of your ability Work INDEPENDENTLY! When finished, work quietly on your Atom Brochures! (Due Friday)

Announcements HW: Due Friday! ◦ Review packet ◦ Atom Brochure Pay your lab fee ($10) in Room 225A All missing work is due Monday 11/2/09 – NO EXCEPTIONS If you need to make up a test or quiz, you need to schedule a time TODAY

Temperature Conversion Two different scales: ◦ Celsius ◦ Kelvin Converting from Celsius to Kelvin: Celsius = Kelvin – 273 Converting from Kelvin to Celsius: Kelvin = Celsius + 273

Examples: 45 ˚C is how many degrees Kelvin? Kelvin = Celsius = = 318 K 285 K is how many degrees Celsius? Celsius = Kelvin – 273 = 285 – 273 = 12˚C