Presentation on theme: "Grade 9 Science Unit 1: Atoms, Elements, and Compounds"— Presentation transcript:
1 Grade 9 Science Unit 1: Atoms, Elements, and Compounds Chapter 2: Elements are the building blocks of matter.
2 ElementsA pure substance that cannot be broken down or separated into simpler substances.Made up of one kind of atom.More than 115 elements known.
3 Chemical SymbolsConsists of one or two letters.Examples:O = OxygenAu = GoldNa = Sodium
4 Elements can be metals, non-metals, or metalloids ShinyMalleableDuctileUsually solidGood conductors of heat and electricity
5 Non-metalsTend to be gases or brittle solidsDullNon-malleable and non- ductilePoor conductors of heat and electricity
6 MetalloidsSolidsShiny or dullMay conduct electricityPoor conductors of heatNon-malleable and non-ductileProperties of both metals and non-metals.
7 Example of Common Elements pg. 41-3 HydrogenIronOxygenSodiumChlorineMercurySilverSilicon
8 The Periodic TableOrganizes elements according to their physical and chemical properties.Developed byDmitri Mendeleevin 1867.
9 Mendeleev’s two main contributions: 1. organizing known elements according to properties and characteristics2. recognizing the need to leave spaces for elements not yet discovered
10 Includes the element’s name, symbol, atomic number and atomic mass.
11 Complete Activity 2-2A pg. 49 Remember the following...#p+ = atomic ##e- = #p+#n = atomic mass - #p+
12 The periodic table is organized into periods and chemical families. Periods: the horizontal rowsFamilies: the vertical columnsElements in the same family have similar physical and chemical properties.
13 Chemical FamiliesAlkali Metals: Family 1Highly reactive with halogensReactive with oxygen and waterLow melting pointsSoft
14 Alkaline Earth Metals: Family 2 Less reactive the alkali metalsBurn in air if heatedProduce bright flamesReact with water
23 Most elements in the same family have the same # of valence electrons This means the same number of electrons in the outermost energy level.The period # = the # of energy levels.The valence shell of the noble gases is FULL; therefore stable.
24 Gaining or losing electrons will allow atoms to achieve a kind of stability. Metals will lose electronsNon-metals will gain them.