The Periodic Table and the Atom
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The Periodic Table and the Atom. Chapter 17.3. SC Standards Covered. Standard PS-2.3 Explain the trends of the periodic table based on the elements’ valence electrons and atomic numbers. Dmitri Mendeleev. arranged elements by atomic mass and similar properties
The Periodic Table and the Atom
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The Periodic Table and the Atom Chapter 17.3
SC Standards Covered • Standard PS-2.3 • Explain the trends of the periodic table based on the elements’ valence electrons and atomic numbers.
Dmitri Mendeleev • arranged elements by atomic mass and similar properties • published the first periodic table • predicted the presence of undiscovered elements
Henry Mosley • arranged elements according to atomic number - periodic law • fixed all the problems of earlier elements being out of order by properties
The Atom and the Periodic Table Groups - vertical rows - the elements in a group have similar properties
Electron Cloud Structure • Electron clouds are arranged by shells • Level 1 – closest to the nucleus • Maximum of 2 electrons • Level 2 – 8 electrons • Level 3 – 8 electrons • Level 4 – 18 electrons
- Elements in the same group have the same number of electrons in their outer energy level
Groups and Valence Electrons • Valence electrons – electrons in the outermost energy level • Group # tells you the number of valence electrons • Group 1 – 1 valence electron • Group 2 – 2 valence electrons • Group 13 – 3 valence electrons • Group 18 – 8 valence electrons
Rows on the Periodic Table • Period – the horizontal row on the periodic table • The period on the periodic table tells how many energy levels it has
2e 8e 2e Group 2 – 2 valence e- Period 3 – 3 energy levels
Drawing Models of Atoms • Determine the number of protons and electrons from the atomic number • Determine the number of neutrons from the mass number • Put the protons and neutrons in the nucleus • Using the period number draw the energy levels the atom has
Put electrons in the shells • First shell: 2 • Second shell: 8 • Third shell: 8 • Check that number of valence electrons matches group number Draw atom models for the following elements: 1.) sulfur – 33 2.) boron - 10
Groups on the Periodic Table • Transition metals - groups 3 – 12 • Alkali metals - group 1 (except hydrogen) • Most reactive metals • Alkaline earth metals - group 2
Oxygen Group:group 16 Halogens - group 17 - most reactive nonmetals Noble gases - group 18 - nonreactive nonmetals
Classifying the Elements • Metals: • shiny, silvery solids • good conductors of heat and electricity • malleable and ductile • located to the left of the stair step line
Nonmetals • gases or dull, brittle solids • poor conductors • right of stair-step line
Metalloids • above and below stair-step line • have properties of both metals and nonmetals