Created by Dmitri Mendeleev ( ) Consists of ~115 element ~90 natural (found in nature) ~25 synthetic (synthesized in the lab) Elements are divided into metals, non- metals and metalloids Metals Physical Properties Luster (shininess) Good conductors of heat and electricity High density (heavy for their size) High melting point Ductile Malleable Chemical Properties Easily lose electrons Corrode easily Non-Metals Physical Properties No luster (dull) Poor conductor of heat and electricity Brittle (breaks easily) Not ductile Not malleable Low density Low melting point Chemical Properties Tend to gain electrons Metalloids have properties of both metals and nonmetals Found on both sides of the staircase Physical Properties Solids Can be shiny or dull Ductile Malleable Conduct heat and electricity better than nonmetals but not as well as metals Periods = rows Numbered 1 7 Elements increase in mass from left to right Groups or Families = columns Numbered 1-18 Have similar chemical & physical properties Alkali metals = group 1 Soft Shiny Silver Very reactive with water Alkaline earth metals = group 2 Shiny, Not as soft as alkali metals Noble Gases = group 18 Generally unreactive (stable) Full outer energy level Non-metals Halogens = group 17 Non-metals Poisonous React easily with alkali metals to form salt (i.e. NaCl) Transition Metals = groups 3-12 Ductile Malleable Conduct electricity & heat An atom is the smallest part of an element that still has the properties of the element Subatomic Particles Electrons negatively charged particles (e - ) Protons positively charged particles (p + ) Neutrons neutral particles (n o ) Protons & neutrons are found in the center of the atom (nucleus) Protons + Neutrons = 99.9% of the atoms mass Energy Levels Electrons occupy the majority of the volume of an atom (99.9%) electrons closest to the nucleus have the least amount of energy, they are held close to the positive charges electrons furthest away from the nucleus have the most energy Level nearest the nucleus can hold 2 electrons 2 nd and 3 rd levels can each hold up to eight Energy levels can be filled, partly filled or empty ParticleSymbolChargeMass (g)Location proton neutron electron ParticleSymbolChargeMass (g)Location protonp+p x Nucleus neutronnono 01.7x Nucleus electrone-e x Orbiting the nucleus The atomic number = # protons The # of protons for each element is constant For an Atom the atomic number = # electrons Elements on the periodic table are arranged according to atomic number ElementSymbolAtomic ## of Protons hydrogen beryllium carbon cobalt krypton ElementSymbolAtomic ## of Protons hydrogenH11 berylliumBe44 carbonC66 cobaltCo27 kryptonKr36 Isotopes: atoms of the same element with the same # of p +, but different # of n o i.e. hydrogen has 1 proton and no neutrons, but 1 in every10, 000 hydrogen atoms contain one proton and one neutron. This isotope is called deuterium (heavy hydrogen), and is used for underwater nuclear reactors To help distinguish between the isotopes, each isotope is given a mass number (#protons + #neutrons) Hydrogen Atomic Mass = 1 Atomic Number = 1 Deuterium Atomic Mass = 2 Atomic Number = 1 The atomic symbol is sometimes shown as mass # element symbol atomic # Mass # = Atomic # + Neutron # # Neutrons = Mass # - Atomic # Atomic Mass or Atomic Molar Mass is the average mass of an elements isotopes. IsotopeMass #Atomic #Proton #Neutron # iron Mn 237 Np carbon-12 IsotopeMass #Atomic #Proton #Neutron # iron Mn Np carbon Homework: Complete Atomic # & Atomic Mass WS Subatomic Particles WS Read Science 10 p Complete Check and Reflect #1-4