+ Bohr Models and Isotopes 01/22 Agenda: 1. Calculating protons, neutrons, and electrons warm up 2. Calculation practice 3. Bohr models 4. Atomic brother Please pick up the handout on the front table and begin filling in the front side key and atom

+ Atomic Structure Practice Bohr Models Valence Electrons Identifying Elements

+ Let’s Review… What was Bohr’s contribution to our understanding of atomic structure? What does a Bohr model look like? How do we determine the number of protons in an atom of an element? How do we determine the number of electrons in an atom of an element? How do we determine the number of neutrons in an atom of an element?

+ Let’s Review… What was Bohr’s contribution to our understanding of atomic structure?

+ Let’s Review… Orbiting electrons Energy levels What was Bohr’s contribution to our understanding of atomic structure?

+ Let’s Review… What does a Bohr model look like?

+ Let’s Review… What does a Bohr model look like? +

+ Let’s Review… What does a Bohr model look like?

+ Let’s Review… How do we determine the number of protons in an atom of an element?

+ Let’s Review… How do we determine the number of protons in an atom of an element? 3 Li Lithium 7 Protons = 3

+ Let’s Review… How do we determine the number of electrons in an atom of an element?

+ Let’s Review… How do we determine the number of electrons in an atom of an element? 3 Li Lithium 7 Protons = 3 Electrons =3

+ Let’s Review… How do we determine the number of neutrons in an atom of an element?

+ Let’s Review… How do we determine the number of neutrons in an atom of an element? Atomic mass – Atomic Number 7 – 3 = 4 neutrons 3 Li Lithium 7 Protons = 3 Atomic mass = 7

+ Bohr Model Practice Create models of atoms of the elements assigned by your teacher using your periodic table for reference.

+ Valence Electrons Reactivity: filling the outer energy level Images: and Valence electrons determine the chemical properties of an element.

+ Isotopes, Ions and Valence Electrons

+ Isotope Atoms of the same element with different numbers of neutrons in the nucleus. Causes a different atomic mass. Example: Taken from:

+ Isotope Question: What changes when you add or take away a neutron from an atom? Answer: The atomic mass changes: it increases when a atom has an extra neutron, and decreases when it has one less neutron.

+ Isotope Question: Which of the atoms below are isotopes for Sodium-12? Hint: Use your periodic table to make calculations and compare. Answer: Sodium’s atomic # is 11, so it has 11 protons and 11 electrons. Choice C has 13 neutrons compared to Sodium-12, so it gained a neutron. Choice:ElementProtonsNeutronsElectrons A.Na1112 B.Na12 11 C.Na111311

+ Ion Atoms that have lost or gained electrons. Causes a different electric charge (positive or negative) Example: Click here for animations describing this further.here Taken from:

+ Ion Question: What changes when you add an electron to an atom? Answer: The electric charge changes to become negatively charged. (Since electrons are negatively charged, adding an electron will cause the atom to be negatively charged.)

+ Ion Question: What changes when you take away an electron to an atom? Answer: The electric charge changes to become positively charged. (Since electrons are negatively charged, taking away an electron will cause the atom to be positively charged.)

+ Ion Question: Which of the atoms below are ions? Hint: Use your periodic table to make calculations and compare. Answer: Oxygen’s atomic number is 8, so a neutral atom would have 8 protons and 8 electrons. Choice A has 9 electrons, making it an ion. Bonus questions: - Is this ion negatively or positively charged? - Which answer choice shows an isotope? Choice:ElementProtonsNeutronsElectrons A.O889 B.O988 C.O878

+ Valence Electrons Electrons in the outermost energy level of an atom that determine the element’s chemical properties. For Elements #1 – 30, there can be 8 valence electrons in the outer shell Taken from:

+ Valence Electrons If an element is stable, it has all 8 valence electrons. Elements with less than 8 valence electrons are reactive. Taken from: lectures/chemistry/chemistr.htm lectures/chemistry/chemistr.htm For example, Sodium, which has 1 valence electron, reacts with Chlorine, which has 7. When the atoms combine, they have a total of 8 valence electrons (1 + 7 = 8) NaCl is a stable molecule, but Na and Cl on their own are reactive.

+ Valence Electrons The periodic table is organized with similar valence electrons in the same columns. Taken from: Which columns would react? Which are stable? Can you predict which will react with each other?

+ Valence Electrons Question: Where are the valence electrons located? Answer: Valence electrons are located in the outer shell.

+ Valence Electrons Question: How many valence electrons need to be in the outer shell for it to be stable? Answer: 8

+ Valence Electrons Question: Which of the atoms would react with each other? Hint: Use your periodic table for help. Notice the Roman Numerals above each column tell you the number of valence electrons: I = 1, II = 2, III = 3, IV = 4, V = 5, VI = 6, VII = 7, VIII = 8. HydrogenHeliumArgon AluminumBromineCalcium Answer: Hydrogen and Bromine would react. Hydrogen is in column 1, so it has 1 valence electron. Bromine is in column 7, so it has 7 electrons = 8!

+ Reactivity & Valence Electrons VIDEO: The Reaction Between Water and the First Group Elements Group 1: Alkali Metals Lithium, Sodium, Potassium, Rubidium, Cesium, Francium

+ Let’s look at their atomic structure. Sodium

+ Let’s look at their atomic structure. Potassium

+ Let’s look at their atomic structure. Cesium