1. SC.A.2.4.5 – Groups, periods and electrons

3. Click hereCompare the reactions of sodium and potassium in water. Why do you think that they reacted similarly? 2

4. The Basics: Atomic Number = # protons (+) 11 Na 22.998 Symbol Energy Level filling 2 8 18 32 Atomic Mass = Mass # (rounded)= protons + neutrons P+ N

5. Lightning Questions How many protons and electrons are found in an atom of Chlorine? How many neutrons are found in an atom of Sodium (Na) that has a mass number of 23 amu? What happens to an atom when you add another proton? How can you change the mass number of an atom of sodium? 4 4

6. 5 Groups and Periods Groups or families are vertical columns in the periodic table Periods are horizontal rows in the periodic table. The zig- zag line separates metals from non-metals Group or family Period With the discovery of isotopes by Mosley in 1909, the Periodic Table was reorganized by increasing atomic number (number of protons). This is modern Periodic Table we use today! 5

7. Valence Electrons These are the electrons found in the last level of an atom. They are the MOST important electrons in determining the reactivity of an atom. Elements with the same number of valence electrons will react similarly. As a rule elements in the same group have the same number of valence electrons. For example: Hydrogen, Lithium, Sodium etc all have 1 valence electron. GROUPS 1A – 8A GIVE THE # OF VALENCE ELECTRONS 6 6

8. 7 Valence Electrons Lithium is #3 in the periodic table. So it has THREE electrons. As we had stated before two electrons are in first level, leaving ONE electron in level 2. So Lithium has ONE valence electron. 7

9. Lightning Questions!!! How many electrons are there in an atom of Sulfur (S)? How many valence electrons are found in an atom of Sulfur? Name an element that would have similar chemical properties to Sulfur. 8 Click here for: Graphing Lab #2 Click here: Post Lab Clip 8

10. Reactivity and the groups Some elements are more reactive than others. Why? Valence electrons! All atoms want a full octet (8 valence electrons). Think about elements like fluorine or chlorine. They’re so close to having 8 valence electrons. Are they reactive? What about elements in group 1? Reactive or not? Group 2 elements? Group 4?

13. Anions = negative (An means to negate) Click here for:Anion clip 10 10

15. FCAT Multiple Choice Sample Questions Mr. Lopez’s science class is playing an educational game to study the periodictable. He gives Trahn a card with some clues to help him identify a particular group on the periodic table. Below is Trahn’s card. 12 Which chemical group…… 1. Reacts with water to form basic solutions 2. Readily combines in nature to form other compounds 3. Loses 2 outer energy level electrons to form +2 ions Trahn’s card describes which group on the periodic table? F. Group 1 G. Group 2 H. Group 16 I. Group 18 FCAT Science Sample Test Book 2007 12

16. FCAT Multiple Choice Sample Questions Julio is given an unknown element to study. After carefully analyzing his element he arrives at the following conclusions. His element has a very low density and when it reacts with other elements it gains 3 electrons to form an anion with a -3 charge. In which of the following groups could we find Julio’s element? A) Group 3 B) Group 5 C) Group 13 D) Group 15 13

17. FCAT Multiple Choice Sample Questions 3. Suppose a scientist makes an unexpected discovery about the possible existence of a new element. The finding does not fit well with the initial hypothesis. The scientist is a member of a team of researchers. If the team behaves according to the best principles of scientific inquiry, which of the following would NOT occur? A) rejection of the finding as being impossible. B) willingness to repeat the studies that led to the finding for confirmation. C) urging the scientist to communicate findings to other researchers. D) insistence on reviewing all data carefully and systematically for any errors. 14