Date: October 7, 2015 Aim #14: What determines an atom’s reactivity? HW: 1)Worksheet- Practice with Atoms and Ions 2)Textbook Guided Reading 2-1 due Tuesday 10/13 Do Now: Warm-Up Notebook DateTitle of ActivityPage # 10/7Analyzing Chemical Formulas26

Meet the Elements

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? An important difference among elements is the # of protons in their atoms. Atomic Number – the number of protons of an element. What is the atomic number of Helium? 2

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? 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 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. What is the mass number of Carbon? How many protons does Oxygen have? 12 8 How many neutrons does Sodium have? 11 Mass number = protons + neutrons

Date: October 8, 2015 Aim #14: What determines an atom’s reactivity? HW: 1)Worksheet- Practice with Ions and Isotopes 2)Textbook Guided Reading 2-1 due Tuesday 10/13 Do Now: Warm-Up Notebook DateTitle of ActivityPage # 10/8Simple Chemistry Review27

What is an Isotope? Isotopes of an element have the same number of protons in their atoms but different numbers of neutrons. C-12 C-13C-14 Mass Number

Brain Pop- Isotopes ndchemistry/isotopes/

Practice Problems 1)How many protons in O-17? 2)What is the atomic number of C-13? 3) What element has an atomic number of 7? 4) What is the mass number of an element with 8 protons, 6 electrons, and 6 neutrons? 5) How many electrons does C-14 have? 8 6 N 14 6

What determines an atom’s reactivity? Electrons Usually it is the electrons in the highest energy level of an atom that determine how that atom reacts 1 st energy level (2 electrons max) 2 nd energy level (8 electrons max) 1st energy level (2 electrons max)

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 1 st energy level can hold 2 electrons and the 2 nd 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? 2)Is He a reactive element? Why? 3)How many free spaces are present in the second level of F? 7 No 1