The Periodic Table. Unit 6

Transcription

1 The Periodic Table Unit 6

2 Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements.

3 Pre-Periodic Table Chemistry was a mess!!! There were at least 55 elements discovered No organization of elements. Varying properties amongst the elements, but some similar trends Difficult to find information.

4 Dmitri Mendeleev In 1869 he published a table of the elements organized by increasing atomic mass

5 Mendeleev s Periodic Table Mendeleev looked at all known elements and began to arrange them Studied Number of valence electrons Similar chemical and physical properties Atomic weight

6 Arranged elements in horizontal rows (periods) and columns (groups or families) Left holes where discovered elements did not fit

7 Dmitri Mendeleev: Father of the Table HOW HIS WORKED Put elements in rows by increasing atomic weight. Put elements in columns by the way they reacted. stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U) was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown.

8 After the discovery of Sc, Ga, and Ge between 1874 and 1885, and the fact that Mendeleev s predictions for their properties were amazingly close to the actual values, his table was generally accepted.

9 Henry Moseley In 1913, through his work with X-rays, he determined the actual atomic number of the elements. He rearranged the elements in order of increasing atomic number (number of protons). His research was halted when the British government sent him to serve as a foot soldier in WWI. He was killed in the fighting by a sniper s bullet, at the age of 28. Memory trick: Mos Pros Modern Periodic Table = atomic number

10 Periodic Table Geography

11 The horizontal rows of the periodic table are called PERIODS.

12 Atoms in the same group have similar chemical properties because they have the same number of VALENCE ELECTRONS! The vertical columns of the periodic table are called GROUPS, or FAMILIES.

13 Metals to the left of the zig zag line Nonmetals to the right of the zig zag line

14 Characteristics of Elements Metals Shiny when smooth and clean Solid at room temp. Good conductors of heat and electricity Malleable Ductile Nonmetals Generally gases or brittle, dull-looking solids Poor conductors of heat and electricity Metalloids Have physical and chemical properties of both metals and nonmetals!

15 Group Numbering 1 2 3A 4A 5A 6A 7A 8A

16 Electronegativity The ability of an element s atoms to attract electrons in a chemical bond Generally Increasing Generally Decreases

17 Electronegativity Most electronegative element is Fluorine (might want to make a note of that) Let s Practice - Between the elements As, Sn and Sb, which is the most electronegative? As Between the elements Sr, Ba and Ra, which is the most electronegative? Sr

18 Ionization Energy The energy needed to remove an electron from a gaseous atom Generally Increasing Generally Decreases

19 Ionization Energy Fluorine has the highest ionization energy of all the elements (might want to make a note) Let s Practice Between Na, Mg, K and Ca, which has the highest ionization energy? Mg Between Pd, Ag and Cd, which has the highest ionization energy? Cd

20 Atomic Radii Half the distance between the nuclei of adjacent, identical atoms in crystals or molecules Generally Decreases Generally Increases

21 Atomic Radii Francium has the largest atomic radius (make a note!) Let s practice Of Li, Be, Na and Mg, which has the largest atomic radius? Na Of S, Se, Te and Po, which has the largest atomic radius? Po