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Lesson 5: Bohr Diagram Atoms and Ions Ions: charged particles (atoms) that have lost or gained electrons. They lose or gain electrons in order to have an electron structure similar to that of a Noble gas. Reason: Noble gases are stable!! Comparing atoms to ions. Atoms Ions - neutral charge - # of electrons equal atomic number - positive or negative charge - # of electrons is different from the atomic number - protons equal atomic number - protons equal atomic number • The atomic mass is the same for both ions and atoms because electrons have such a small mass that they can be ignored. Draw a Bohr diagram. To draw Bohr Diagrams: 1. Draw the nucleus as a solid circle. 2. Put the number of protons (atomic number) in the nucleus with the number of neutrons. 3. Place the number of electrons in orbits around the nucleus by drawing circles around the nucleus. 1st shell – 2 e-, 2nd shell – 8 e-, 3rd shell – 8 e-, 4th shell – 18 eFor oxygen. 16 8 O 8 p+ 8 n0 For sodium. 22.99 Na 11 11 p+ 12 n0 Your turn: draw these diagrams for the first twenty elements. METALS: -tend to lose electrons. -become positively charged. -the size of the positive charge is determined by the number of electrons lost. -the number of electrons lost is determined by the proximity to the nearest Noble gas. -named by using the full metals name and adding ion at the end. eg: Magnesium is a group two element. 12 electrons. An atom of magnesium has ____ 10 electrons. neon and it has ______ The nearest Noble gas is ________ An ion of magnesium must also have _______ electrons 10 because this is a more stable configuration. This results in magnesium having a net charge of 2+. It is named ___________________ magnesium ion NON-METALS: -tend to gain electrons. -become negatively charged. -the size of the negative charge is determined by the number of electrons gained. -the number of electrons gained is determined by the proximity of Noble gas. -named by dropping the ending and adding an ‘ide’ ending Eg: Chlorine. 17 electrons. An atom of chlorine has _______ 18 argon and it has ______ The nearest Noble gas is ________ electrons. 18 An ion of chlorine must also have _______ electrons because it is more stable. This results in chlorine having a net charge of 1-. The name is __________ chloride Valence Electrons Elements in the same family have the same number of outermost electron. These electrons are called valence electrons. Valence electrons are responsible for chemical reactions. Try this: 1. How many electrons does Al atom possess? 13 2. How many valence electrons does Al atom possess? 3 Octet Rule States that atoms bond in such a way as to have eight electrons in their valance energy level. Atoms try to bond to become stable like the noble gasses. They will lose or gain electron in order to have eight in their last energy orbital. Look back at the Aluminum Atom It has 3 valence electrons. If it wants to become stable, it has to lose 3 electrons and it will have the same number of electrons as Neon. That is why Aluminum ion is Al 3+ Check This Out There is a pattern in the periodic table for the charges. Try this: What is the ionic charge for: Alkali Alkaline Earth Metals Halogens Noble Gasses +1 _______ +2 _______ _______ -1 _______ 0 Homework: 1. Finish drawing Bohr Diagram for the first 20 elements. 2. Read pg 35, 38 and complete questions 3, 5, 6, 9, 10, 12