The Periodic Table and the Atom

1. The Periodic Table and the Atom Chapter 17.3

2. SC Standards Covered • Standard PS-2.3 • Explain the trends of the periodic table based on the elements’ valence electrons and atomic numbers.

3. Dmitri Mendeleev • arranged elements by atomic mass and similar properties • published the first periodic table • predicted the presence of undiscovered elements

5. Henry Mosley • arranged elements according to atomic number - periodic law • fixed all the problems of earlier elements being out of order by properties

6. The Atom and the Periodic Table Groups - vertical rows - the elements in a group have similar properties

7. 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

8. - Elements in the same group have the same number of electrons in their outer energy level

9. 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

10. 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

11. 2e 8e 2e Group 2 – 2 valence e- Period 3 – 3 energy levels 

12. 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

13. 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

14. Groups on the Periodic Table • Transition metals - groups 3 – 12 • Alkali metals - group 1 (except hydrogen) • Most reactive metals • Alkaline earth metals - group 2

15. Oxygen Group:group 16 Halogens - group 17 - most reactive nonmetals Noble gases - group 18 - nonreactive nonmetals

16. 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

17. Nonmetals • gases or dull, brittle solids • poor conductors • right of stair-step line

18. Metalloids • above and below stair-step line • have properties of both metals and nonmetals