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2/27/12 - Bellringer What is the joke in this comic? Atomic Structure Review Atoms are made up of protons, neutrons, and electrons Individually, atoms have the same number of p+ and e- Atomic Structure Review If an element has 8 protons, how many electrons does it have? If an element has 53 electrons, how many protons does it have? Atomic Structure Review The number of electrons in an atoms valence shell is NOT the total number of electrons in that atom (except for H and He) Valence shell = outer electron shell 22.2 Notes – Types of Bonds Objective Describe ionic and covalent bonds Ion An atom that has lost or gained electrons A charged particle because it has more or fewer electrons than protons Atoms lose or gain to meet a standard—a stable energy level Sports drinks – Electrolytes = ions in found in blood How bonds form The positive and negative charges are not balanced on their own It is the electric forces between oppositely charged particles that hold compounds together A Bond Forms - KI A neutral atom of potassium has one electron in its outer level Not a stable outer energy level Potassium often forms compounds with halogens Alkalis (Group 1) often form compounds with Halogens (Group 17 / 7A) Potassium atom has become an ion Loses an electron (drops one energy level), becomes positively charged One less electron in the atom than protons in the nucleus Ion = K+ The 1+ charge is shown as a superscript written after the element’s symbol to indicate its charge Iodine atom also undergoes a change Iodine has 7 electrons in its outer energy level Iodine atom wants to gain an electron to fill its outer energy level No longer neutral because it has gained an extra negative particle Has a charge of –1 and is called a iodide ion, written as I- Cation = positive ion Loses electrons Anion = negative ion Gains electrons Potassium iodide Ionic Bonds When ions attract due to their opposite charges In an ionic bond a transfer of one or more electrons takes place and large amounts of energy are released If an element loses electrons, one or more elements must gain an equal number of electrons to maintain the neutral charge http://www.youtube.com/watch?v=c-nMmwfTV-w Formation of Ionic Bond Magnesium reacts with chlorine Magnesium atom loses 2 electrons and becomes a positively charged ion, Mg2+ Two chlorine atoms gain one electron each and become negatively charged ions, Cl- Ionic Bonds Zero net charge = Neutral compound Positive charge balances with negative charge Metal + nonmetal Elements on opposite sides of periodic table