How are days organized?

Dmitri Mendeleev Russian 1860’s The Person Who Organized the Elements Dmitri Mendeleev Russian 1860’s

Mendeleev Teacher at St. Petersburg University. Was working on a textbook for his Chemistry students. He organized the 63 elements known at the time.

His Criteria Increasing atomic mass. Physical and Chemical Properties.

Mendeleev’s Predictions He left spaces on the table for undiscovered elements. He predicted the properties of elements that had not yet been discovered. Very cool!

This is Neon. He is a stable atom. This makes him happy! All atoms want to have a full outer shell of electrons. This is 2 on the first shell and 8 on the next couple of shells. This is Neon. He is a stable atom. This makes him happy! Why is he stable? valence electrons: the number of e in the outer shell

What could you suggest to help them out? fluorine lithium beryllium These atoms are all unstable as they do not have full outer shells of electrons. What could you suggest to help them out? sodium chlorine oxygen hydrogen

Periodic Trends Groups 1 to 18 look at electron arrangement for the first 20 elements G1 G2 G3 to G15 G16 G17 G18

Mg + O = MgO Metal gas Metal oxide 2Mg + O2 2MgO Heat Mg2+ O2-

THEORY: What’s the use of electron arrangements?   Atoms join by using valence electrons. Atoms in group 18 have full levels and don’t join up. They are noble gases and unreactive Other atoms either take, give or share electrons to get a FULL outer shell which would make them stable. Atoms with 1,2 or 3 valence electrons prefer to LOSE Atoms with 4 valence electrons like to SHARE their electrons Atoms with 5,6 or 7 valence electrons TAKE or share other electrons. Atoms with 8 valence electrons don’t usually do anything, they are stable as they are!!

Metals Gases GROUPS PERIODS Halogens Noble Gases Transition Metals Alkali Metals Alkaline Earth Metals

ALKALI METALS Group 1 Hydrogen is not a member, it is a non-metal 1 electron in the outer shell Soft and silvery metals Very reactive, esp. with water Conduct electricity Image: http://www.learner.org/interactives/periodic/groups2.html

ALKALINE EARTH METALS Group 2 2 electrons in the outer shell White and malleable Reactive, but less than Alkali metals Conduct electricity

TRANSITION METALS Groups (3 to 12) in the middle Good conductors of heat and electricity. Some are used for jewelry. The transition metals are able to put up to 32 electrons in their second to last shell. Can bond with many elements in a variety of shapes.

Halogens Group 17 7 electrons in the outer shell All are non-metals Very reactive are often bonded with elements from Group 1

Noble Gases Group 18 Exist as gases Non-metals 8 electrons in the outer shell = Full Helium (He) has only 2 electrons in the outer shell = Full Not reactive with other elements