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Periodic Table Section 18.3.

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Presentation on theme: "Periodic Table Section 18.3."— Presentation transcript:

1 Periodic Table Section 18.3

2 Periodic Table Periodic- Repeated in a pattern
Elements are ordered by: increasing atomic number changes in physical & chemical properties Mendeleev- Ordered elements by atomic mass Left blank places in his table to line up elements according to their properties Elements were later discovered and fit into the places he left blank

3 Periodic Table Moseley- organized elements by atomic number rather than atomic mass Same arrangement as today Groups/Families- vertical columns of the periodic table Electrons Around the nucleus in an electron cloud Energy levels dictate location of electrons Closer to nucleus = less energy Fill energy levels from inner to outer levels

4 Electrons Electrons in outer shell – determine chemical properties of elements Complete outer shell- needs 8 electrons to be stable Energy levels and # of electrons in each: Level 1 Holds 2 Level 2 Holds 8 Level 3 Holds 18 Level 4 Holds 32

5 Valence Electrons Group 1A – 8A have 1-8 valence electrons- See periodic table for details Electron dot diagrams- A symbol of an element surrounded by dots to represent electrons in the outer energy level Properties of elements in the same group- similar due to same # of valence electrons

6 Arrangement of Periodic Table
Halogens- group 7A Likely to react with Alkali metals- group 1A Rows of Periodic Table- periods Properties of metals- lustrous, conductive for heat and electricity, malleable, ductile (located in middle and left of periodic table) Properties of nonmetals- brittle, often gases, don’t conduct Properties of metalloids- have properties of both metals and nonmetals

7 Building Blocks of Universe
Hydrogen and Helium Combine to form elements with larger atomic numbers – can only occur through nuclear reactions

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