2A Seating Chart

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6. Friday, Jan. 10th: “A” DayMonday, Jan. 13th: “B” DayAgenda • Collect movie worksheet • Begin Chapter 5: “Ions and Ionic Compounds” • Sec. 5.1: “Simple Ions” • Octet rule, ion, cation, anion • In-Class: Section 5.1 review, pg. 165: #1-13 • Homework: • “Ions and Subatomic Particles” worksheet • Concept Review: “Simple Ions” Next time: Quiz over section 5.1

7. Chemical Reactivity • How much an element reacts depends on its electron configuration. • Noble gases are the least reactive elements because their outer energy levels are full with 8 electrons. (except He, which is full with 2) • In most chemical reactions, atoms try to match the electron configurations of the noble gases by either gaining or losing electrons. • Most atoms want to become “noble”.

8. Chemical Reactivity • Octet Rule: a concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty valence shells or full valence shells of eight electrons. “8is Great!”

9. *Alkali Metals and Halogens are the Most Reactive Elements* • As members of Group 1, alkali metals have only 1 electron in their outermost energy level. • By losing that 1 electron, an alkali metal can get an electron configuration like a noble gas, with 8 electrons in its outermost energy level. - 1 electron 1s22s22p63s23p64s1 1s22s22p63s23p6 • Which alkali metal is this? Potassium (K)

10. *Alkali Metals and Halogens are the Most Reactive Elements* • Remember, potassium’s electron configuration was: 1s22s22p63s23p64s1 • Question: Why doesn’t potassium gain 7 electrons to achieve a stable octet instead of losing 1? • Answer:Removing 1 electron requires far less energy than adding 7 electrons.

11. Alkali Metals and Halogens are the Most Reactive Elements • As members of Group 17, the halogens have 7 electrons in their outermost energy level. • By gaining 1 electron, a halogen can get an electron configuration like a noble gas, with 8 electrons in its outermost energy level. + 1 electron 1s22s22p63s23p5 1s22s22p63s23p6 • Which halogen is this? Chlorine (Cl)

12. Valence Electrons • After it loses one electron, potassium has the same electron configuration as chlorine does after it gains one electron. • Both are the same as the noble gas argon. 1s22s22p63s23p6 • The atoms of many elements become stable by achieving the electron configuration of a noble gas. • Remember, the electrons in the outermost energy level are called valence electrons.

13. The Periodic Table Reveals an Atom’s Number of Valence Electrons • To find out how many valence electrons an atom has, check the periodic table. • Magnesium, Mg, has the shorthand electron configuration: [Ne]3s2 • The outermost energy level is the 3rd energy level. • This means that a magnesium atom has two valence electrons, located in the 3s orbital.

14. The Periodic Table Reveals an Atom’s Number of Valence Electrons • The shorthand electron configuration of phosphorus, P, is: [Ne]3s23p3 • The outermost energy level is the 3rd energy level. • This means that each phosphorus atom has five valence electrons: two in the 3s orbital and three in the 3p orbital.

15. Atoms Gain or Lose Electrons to Form Stable Ions • All atoms are uncharged because they have equal numbers of protons and electrons. • For example, a potassium atom has 19 protons and 19 electrons. • After losing one electron, potassium still has 19 protons but now only has 18 electrons. • Because the numbers are not the same, there is a net electrical charge.

16. Atoms Gain Or Lose Electrons to Form Stable Ions • Ion:an atom, radical, or molecule that has gained or lost one or more electrons and has a negative or positive charge. • The following equation shows how a potassium atom forms an ion with a 1+ charge. K  K+ + e • Cation: an ion that has a positive charge.

17. Atoms Gain Or Lose Electrons to Form Stable Ions • In the case of chlorine, far less energy is required for an atom to gain one electron rather than lose its seven valence electrons to become stable. • The following equation shows how a chlorine atom forms an ion with a 1− charge. Cl + e → Cl • Anion: an ion that has a negative charge

18. Characteristics of Stable Ions • Both an atom and its ion have the same number of protons and neutrons, so the nuclei are the same. • But, an atom and its ion have different numbers of electrons. • The chemical properties of an atom depend on the number and configuration of its electrons. • So, an atom and its ion have different chemical properties.

19. Many Stable Ions Have Noble-Gas Configurations (pg. 162)

20. Some Stable Ions Do Not Have Noble Gas Configurations • Transition metals often form ions without complete octets. • The stable transition metal ions are all cations. • Some elements, mostly transition metals, can form several stable ions that have different charges…

21. Some Stable Ions Do Not Have Noble Gas Configurations (pg. 163)

22. **Metals Form Cations** • Nearly all metals form cations, which means they lose electrons. For example, magnesium metal, Mg, has the electron configuration: 1s22s22p63s2 • To achieve a noble-gas configuration, magnesium must lose two electrons. • Losing two electrons requires less energy than gaining six. Atoms are lazy, just like us!

23. **Non-metals Form Anions** • The atoms of all non-metal elements form anions, which means they gain electrons. For example, oxygen, O, has the electron configuration 1s22s22p4 • To achieve a noble-gas configuration, oxygen must gain two electrons. • Acquiring two electrons requires less energy than losing six.

24. In-Class/Homework • In-Class: • Section 5.1 review, pg. 165: #1-13 • Homework: • “Ions and Subatomic Particles” WS • Concept Review: “Simple Ions” Next time: Quiz over Section 5.1

25. Door 4A Seating Chart Wi ndows Front of Room