Mendleev and discovery of periodic table

Periodic table explanation

1. Periodic Trends Elemental Properties and Patterns

2. The Periodic Law Dimitri Mendeleev was the first scientist to publish an organized periodic table of the known elements. He was perpetually in trouble with the Russian government and the Russian Orthodox Church, but he was brilliant never-the-less.

3. The Periodic Law Mendeleev not only predicted the existence of 2 (at the time) undiscovered elements, but he predicted the properties too, and he was right! He was very accurate in his predictions, which led the world to accept his ideas about periodicity and a logical periodic table.

4. The Periodic Law Mendeleev ordered a periodic table according to atomic mass, which makes sense (look at a few in a row)

5. The Periodic Law However this does not work for a 100% of the elements

6. In 1913, Henry Moseley decided to arrange the periodic table by the number of protons, a.k.a The atomic number This is the version that we use today The Periodic Law

7. The Periodic Law Mendeleev and Moseley understood the ‘ Periodic Law ’ which states: When arranged by increasing atomic number , the chemical elements display a regular and repeating pattern of chemical and physical properties.

8. The Periodic Law Atoms with similar properties appear in groups or families (vertical columns) on the periodic table. They are similar because they all have the same number of valence (outer shell) electrons , which governs their chemical behavior.

9. A Different Type of Grouping There is a way of classifying element: Metals Nonmetals Metalloids or Semi-metals.

10. Metals, Nonmetals, Metalloids

11. Metals, Nonmetals, Metalloids There is a zig-zag or staircase line that divides the table. Metals are on the left of the line, in blue . Nonmetals are on the right of the line, in orange .

12. Metals, Nonmetals, Metalloids Elements that border the stair case, shown in purple are the metalloids or semi-metals. There is one important exception. Aluminum is a metal

13. Metals Metals are lustrous (shiny), malleable, ductile, and are good conductors of heat and electricity. They are mostly solids at room temp. What is one exception?

14. Nonmetals Nonmetals are the opposite. They are dull, brittle, nonconductors (insulators). Some are solid, but many are gases, and Bromine is a liquid.

15. Metalloids Metalloids, aka semi-metals are just that. They have characteristics of both metals and nonmetals. They are shiny but brittle. And they are semiconductors . What is our most important semiconductor?

16. Group IA: The Alkali Metals The metals in Group IA (Li, Na, K, Rb, Cs, and Fr) are called the alkali metals because they all form hydroxides (such as NaOH) that were once known as alkalies . The electron configurations of the alkali metals are characterized by a single valence electron.

17. Group IA: The Alkali Metals As a result, the chemistry of these elements is dominated by their tendency to lose an electron to form positively charged ions (Li + , Na + , K + ). The more electronic shielding means the higher the reactivity because the outer electron becomes easier to lose, therefore the reactivity increase down the group.

18. Group VIIA: The Alkali Metals The non - metals in Group VIIA (F, Cl, Br, I and At) are called halogens because they react rapid;y with metals to form salts (such as NaCl). The electron configurations of the halogens are characterized by a seven valence electrons.

19. Group VIIA: The Alkali Metals As a result, the chemistry of these elements is dominated by their tendency to gain an electron to form negatively charged ions (F - , Cl - , I - ). The more electronic shielding means the lowerr the reactivity because the outer electron becomes harder to gain, therefore the reactivity decrease down the group.

20. Group VIIIA: The NOBLE GASES The noble gases were once called inert gases because they were thought to be completely unreactive. The low reactivity of noble gases leads to some special uses. Helium, a noble gas, is used to fill blimps because it has a low density and is not flammable. .