Objective 4.03 Objective 4.03: Explain how the Periodic Table is a model for: • Classifying elements • Identifying the properties of elements

Mendeleev’s Periodic Table Mendeleev’s periodic table arranges elements according to the atomic mass Atomic mass is the number of protons and neutrons Elements with similar properties are found in the same column Periodic table—chart that organizes information about all of the known elements according to their properties http://www.aip.org/history/curie/periodic.htm

Today’s Periodic Table 1913, Henry Moseley showed that atomic number was the most important feature because it is what is responsible for chemical properties Electron configuration determines chemical properties Today elements are in order of the atomic number Atomic number—number of protons in the nucleus of an atom

Today’s Periodic Table

Periodic Table Chemical family or group is the Vertical column on the periodic table All have similar properties, numbered 1-18 and from 1A to 8A, all have same number of valence electrons Groups 1-2(IA-IIA) and 13-18(IIIA-VIIIA) are the main groups Groups 3-12 are called transition elements Elements on the left side of the periodic table are metals, except hydrogen Elements on the right side of the periodic table are nonmetals

Today’s Periodic Table

Properties of Nonmetals Properties of Metal Properties of Nonmetals Solid at room temperature, except mercury, which is a liquid Most are gases, except bromine, which is a liquid Malleable(shaped) and ductile (drawn into wire) Brittle in solid phase Have luster (shiny) Normally dull Have high thermal and electrical conductivity Are poor conductors of heat and electricity Tend to lose electrons in chemical reactions Tend to gain electrons in chemical reactions Reactivity describes how likely an element is to form bonds with other elements

Group 1 and Hydrogen Hydrogen is found above Group 1 but doesn’t belong to any group Placed here because it only has one valence electron. It’s properties are different from the other groups.

Alkali Metals Group 1 (Alkali Metals) on periodic table Most chemically active One electron in the outer shell Easily combine with nonmetals Reactivity of the metal decreases with increasing atomic number Reactivity increases

Alkaline Earth Metals Group 2 (Alkaline Earth Metal) on the periodic table Highly reactive but less reactive than group 1 Reactivity of the metal increases with increasing atomic number Reactivity increases

Transition Metals Group 3 –12 (transition metals) on the periodic table Generally hard solids with high melting points Often form colored ions

Metalloids Metalloids Found along the zigzag between the metals and nonmetals on the periodic table Have properties of both metals and nonmetals http://www.gordonengland.co.uk/elements/metaloids.htm

Halogens Group 17 (Halogens) on the periodic table Most reactive of the nonmetals Reactivity in nonmetals increases as atomic number decreases Fluorine (F) is the most reactive Halogens react with alkali metals to form salts Elements in this family are all states of matter Fluorine(Fl) and Chlorine—gases Bromine (Br)—liquid Iodine (I) and Astatine (At) are solids at room temperature

Noble Gases Group 18 (Noble Gases) on periodic table Least reactive of all elements Inert—unable to react chemically

Periods Periods are the rows Elements in the same period have the same number of electron orbits(shells) Atoms are similar sizes Electronegativity (tendency to attract electrons) increases from left to right http://www.chem4kids.com/files/elem_pertable.html

Periodic Table http://www.periodictable.com/ http://www.bbc.co.uk/schools/ks3bitesize/science/chemical_material_behaviour/particle_model/revise1.shtml