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Date: October 7, 2015 Aim #14: What determines an atom’s reactivity? Do Now: Warm-Up Notebook Date 10/7 Title of Activity Analyzing Chemical Formulas Page # 26 HW: 1) Worksheet- Practice with Atoms and Ions 2) Textbook Guided Reading 2-1 due Tuesday 10/13 Meet the Elements https://www.youtube.com/watch?v=d0zION8xjbM Review of Atoms: P N Nucleus (protons and neutrons) Electrons The protons and neutrons have a much greater mass than the electrons. Where are the electrons? The electrons continually move around the nucleus at great speed. The attraction between the (-) charged electrons and the (+) charged protons keeps the electrons close to nucleus. What are the differences between elements? What is the atomic number of Helium? 2 An important difference among elements is the # of protons in their atoms. Atomic Number – the number of protons of an element. Can we find this information on the Periodic Table? **Notice, that no two elements have the same atomic number. Atoms tend to be electrically neutral What does that mean? Atoms, if left alone, typically have the same number of protons and electrons. How many protons should this atom have if it is electrically neutral? 11 What is its atomic number? 11 What is an Ion? An atom that has a positive or negative charge due to a loss or gain of ELECTRONS! Cation (+ Ion) – due to loss of an electron. Anion (- Ion) – due to gain of an electron. Brain Pop- Ions https://www.brainpop.com/science/mattera ndchemistry/ions/ Atomic Number vs. Mass Number The atomic number is the number of protons found in an element. The mass number is the number of protons plus the number of neutrons. Mass number = protons + neutrons What is the mass number of Carbon? How many protons does Oxygen have? 12 8 How many neutrons does Sodium have? 11 Date: October 8, 2015 Aim #14: What determines an atom’s reactivity? Do Now: Warm-Up Notebook Date 10/8 Title of Activity Simple Chemistry Review Page # 27 HW: 1) Worksheet- Practice with Ions and Isotopes 2) Textbook Guided Reading 2-1 due Tuesday 10/13 What is an Isotope? C-12 C-13 Mass Number C-14 Isotopes of an element have the same number of protons in their atoms but different numbers of neutrons. Brain Pop- Isotopes https://www.brainpop.com/science/mattera ndchemistry/isotopes/ Practice Problems 1)How many protons in O-17? 8 2)What is the atomic number of C-13? 6 N 3) What element has an atomic number of 7? 4) What is the mass number of an element with 14 8 protons, 6 electrons, and 6 neutrons? 5) How many electrons does C-14 have? 6 What determines an atom’s reactivity? Electrons 2nd energy level (8 electrons max) 1st energy level (2 electrons max) 1st energy level (2 electrons max) Usually it is the electrons in the highest energy level of an atom that determine how that atom reacts How do we know if an element is reactive? If an element has partly-filled outer energy levels This condition makes these elements chemically reactive. Rules in filling energy levels: 1)Determine the number of electrons the atom has. 2)Remember, the 1st energy level can hold 2 electrons and the 2nd energy level can hold 8 electrons. 3) Fill the lowest energy levels first. Practice Problems: 1)If an atom has 9 electrons, how many electrons are in the second energy level? 7 2)Is He a reactive element? Why? No 3)How many free spaces are present in the second level of F? 1