PERIODIC TABLE TRENDS

1. September 15 PERIODIC TABLE TRENDS

2. Mendeleev & Moseley • Dmitri Mendeleev , a Russian chemist, noticed that when the elements were arranged by atomic mass, there was a periodic pattern in properties • He left blank spaces open for new elements to be discovered • He was one of the first to arrange the elements in an organized table • His arrangement had its faults though…

4. When new elements were discovered, it became apparent that they didn’t fit into Mendeleev’s table properly • When arranged by mass, the properties did not correspond • Moseley (1913) – Arranged periodic table by atomic number • Elements close to one another have similar properties

6. Periodic Law • Periodic Law: there is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number

8. How to read those numbers… • Atomic Mass: Approx. the mass of the protons in the element • 1 atomic mass unit (amu)= mass of 1 Carbon 12 atom • Atomic Number: # of protons in the nucleus • The atomic number increases by 1 as you go across a row • Also the number of electrons in the element if it is neutral

9. What is in an element/atom? • Protons: Positive Charge (+) • Neutrons: No Charge • Electrons: Negative Charge (-) • Protons +Neutrons make up a nucleus • Electrons circle around the nucleus in orbitals • In general, #protons=#electrons (neutral) • Also #neutrons= atomic mass-atomic number • If they differ in neutrons, it is called an isotope • C12, C13, C14

11. So… • If elements are ordered in the periodic table by atomic number, then they are also ordered according to the number of electrons they have. • The lineup starts with hydrogen, which has one electron. • Helium comes next in the first horizontal row because helium has two electrons. Lithium has three.

12. Valence Electrons • In an atom there are multiple orbitals (think planets) • Valence electrons: electrons in the outer most orbital…these determine the chemical properties of the element

13. Back to the periodic table • Period: Horizontal Row (think sentence) • Numbered from top to bottom • Group/Family: Column/Vertical • Numbered from left to right

15. Proximity Matters • Elements in the same group have characteristics similar to each other, yet different from the other elements in the periodic table. • Similarities occur because elements in the same group have the same number of valence electrons

16. Names & Organization • Periodic table is divided into 4 main groups • Representative or main-group elements • Transition metals • Lanthanide series • Actinide series

17. Groups 1A – Alkali metals • Very reactive • Explosive reactions with water • One valence electron • All metals • Groups 2A – Alkaline Earth Metals • Quite reactive • Two valence electrons • All metals

18. Groups 3A – Boron Family • Varies from semi-metallic to non-metallic in properties • Three valence electrons • Group 4A – Carbon Family • Varies from non metallic to metallic in properties • Four valence electrons

19. Group 5A – Nitrogen Family • Varies from non-metallic to metallic properties • Five valence electrons • Groups 6A – Oxygen Family • Mostly non-metallic • Six valence electrons • Group 7A – Halogens • All are non-metallic and make colorful gases • Seven valence electrons

20. Group 8A – Noble gases • All non metals and highly unreactive • Eight valence electrons • Transition metals • All have metallic properties • Valence number varies • Lanthanoids & Actinoids • Radioactive, many are non-natural or man-made • Valence number varies

22. Metallic Character Metallic Character • Element on the left side of the periodic table are metals, while those on the right side are non metals. • Elements that touch the dividing line between metals and nonmetals are called metalloids • Metallic character increases as you move down a column and across a row to the left

24. Reactivity Reactivity • Reactivity for metallic element increases as you move down a column and across a row to the left • The most reactive metal is Francium (bottom, left corner) • Reactivity for nonmetal increases as you move up a column and across a row to the right • The most reactive nonmetal is Fluorine (top, right corner)

26. Ionization Energy • Ionization Energy • The energy needed to remove the outermost electron from an element (increases dramatically with successive removals) • Ionization energy depends on the number of valence electrons and the size of the atom • Elements with nearly full valence shells will have higher ionization energy than those with nearly empty valence shells • Larger elements will have a lower ionization energy than smaller elements

27. Ionization energy increases as you move up a column and across a row to the right.

29. Electronegativity • Electronegativity (similar trend to ionization) • Ability of an element to attract shared electrons to itself • Depends on the number of valence electrons and the size of the element • Increases as you move up a column and across a row to the right

31. Atomic Radius Atomic Radius • Close approximation of the relative size of an atom • Determined by finding the distance from the center of an atom nucleus to it’s outermost electron • Increases as you move down a column • Each step down in a column increases the number of orbitals (electron shells) • Increases as you move across a row to the left • Decreasing the number of protons in the nucleus causes the electrons to be held more loosely

33. How size changes… Ionic Size • Size of an atom when electrons are added or removed • Electrons removed atom become smaller • Electrons added atoms become larger

34. Your Project • http://www.azuregrackle.com/periodictable/table/

35. Your Special Element Rubric Total Points: 60 Due Tues Nov. 23 Total = 60 points