2 Valence Electron and Bonding What are valence electrons?Electrons that have the highest energy level and are held more looselyThe number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms
3 Valence Electrons What is an electron dot diagram? The symbol for the element surrounded by dotsEach dot stands for one valence electronEach element has a specific number of valence electronsAtoms are more stable and less likely to react when they have eight valence electronsThese elements do not easily form compounds
4 Valence Electrons How do elements become stable? Atoms usually react in a way that makes each atom more stable1) They either increase their valence electrons to eight2) Or, the atom gives up loosely held valence electronsAtoms that react by loosing valence electrons become chemically bonded with other atomsA chemical bond is the force of attraction that holds two atoms together as a result of the rearrangement of electrons between themWhen atoms bond, electrons are transferred from one atom to another
5 Periodic Table How is the periodic table organized? By atomic number, the arrangement of electrons in atoms, and the number of protons in the nucleus of an atomAs the atomic number increases, the number of electrons also increasesA period ends when the highest energy level has eight electronsThe elements within a group always have the same number of valence electrons, therefore they have the same properties
6 Periodic TableNoble Gases: Group 18 and atoms of these elements have eight valence electrons which is why they do not react easily, except for Helium which has 2Reactive Metals and Nonmetals: Noble gases in group 17, only have seven valence electrons. A gain of just one more electron gives these atoms the stable number of eight electrons.Metals in Group 1 have only one valence electron, therefore react by losing an electron to become more stable.
7 Periodic TableOther Metals: How reactive a metal is depends on how easily its atoms lose valence electrons. Atoms in group 2 are more likely to lose electrons than in group 3-12.Other Nonmetals: All of the nonmetals have four or more valence electrons, so react by gaining electrons to become more stable. Nonmetals can combine with other nonmetals by sharing electrons.Hydrogen: Hydrogen is located in Group 1 because it only has one valence electrons, but it is a nonmetal so it reacts a lot differently then other elements in Group 1
8 Ionic BondingAtoms with 5, 6, or 7 valence electrons usually become more stable when the number increases to 8Atoms with 1, 2, 3, or 4 valence electrons usually become more stable when it loses electronsWhen these two type of atoms combine, they form an ionic bondHow does an ion form?When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and become a negative ion.What is a polyatomic ion?Ions that are made of more than one atom. It is a group of atoms that react as a unit.
9 Ionic BondingSodium has 1 valence electron and chlorine has 7 valence electronsWhen sodium’s valence electrons are transferred to chlorine, both atoms become an ionThe sodium become the positive ion and chlorine become the negative ionWhat is an ionic bond?The attraction between two oppositely charged ionsIonic bonds form as a result of the attraction between positive and negative ionsA compound that consists of a positive ion and a negative ion like sodium chloride, is called an ionic compound
10 Chemical Formulas and Names What is a chemical formula?A combination of symbols that shows the ratio of elements in a compoundEx. MgCl2When ionic compound forms, the ions come together in a way that balances out the charges on the ionsTwo chloride ions, each with a charge of -1 will balance the charge on the magnesium ion. That is why the formula for magnesium chloride is MgCl2.A subscript tells you the ratio of elements in the compound. The ratio for magnesium chloride is 2 to 1.
11 Naming Ionic Compounds How do you name ionic compounds?For an ionic compound, the name of the positive ion comes first, followed by the name of the negative ion. The name of the first ion is usually a metal, unless a polyatomic ion exists such as NH4 which is ammonium chlorideRule 1-If the negative ion is a single element, the end of the naming of the compound is IDEEX - Sodium ChlorideRule 2-If the negative ion is polyatomic, its name usually ends in ATE or ITE
12 Properties of Ionic Compounds What are some properties of ionic compounds?HardBrittle CrystalsHigh Melting PointsWhen dissolved in water or melted, they conduct electricity.The ions form a orderly, three dimensional crystal arrangementWhen ionic crystals dissolve in water, the bonds between ions are broken