Download presentation
Presentation is loading. Please wait.
Published byPatrick Hodges Modified over 9 years ago
1
THE PERIODIC TABLE BRIEF HISTORY
2
Dmitri Mendeleev (1869, Russian) –Organized elements by increasing atomic mass. –Elements with similar properties were grouped together. –There were some discrepancies. –Predicted properties of undiscovered elements.
3
Henry Mosely (1913, British) Organized elements by increasing atomic number. Resolved discrepancies in Mendeleev’s arrangement.
4
I. ORGANIZATION of ELEMENTS Three major categories: -Metals -Non-metals -Metalloids
5
METALS Shiny Lustrous Various colors, but most are silvery Good conductors of heat & electricity Most are solids at room temperature that are: –Ductile –Malleable Mercury is a liquid at room temperature. NON-METALS Dull, not shiny. Various colors Poor conductors of heat & electricity (good insulators) Are solids, liquids & gases. Liquids: Br 2 Gases: Noble gases, H 2, N 2, O 2, F 2, and Cl 2 Remaining elements are solids.
6
METALLOIDS Elements that border the “staircase” on the periodic table. Have properties of both metals & non-metals. Their behavior depends on what they are bonded to chemically. –They behave like a metal when bonded to a non- metal. –They behave like a non-metal when bonded to a metal.
7
II. Predicting Oxidation Numbers Oxidation State: -# of electrons an atom will gain or lose to become stable. Metals always have positive (+) oxidation states. Nonmetals have negative (-) oxidation states.
8
s – Block Metals GROUP 1 Alkali Metals -have 1 valence electron and s 1 configuration. -lose 1 electron to become stable. -have oxidation number of +1 (charge) GROUP 2 Alkaline Earth Metals -have 2 valence electrons and s 2 configuration. -lose 2 valence electrons to become stable. -have oxidation number of +2 (charge)
9
p-Block Metals Must lose electrons; have 2 possibilities: 1.Remove ALL valence electrons 2.Remove only “p” valence electrons (all at once)
10
d – Block Metals Must lose electrons; have several possibilities: 1.FIRST, remove ALL valence electrons 2.Then, remove “d” electrons, one at a time (until stable)
11
Non-Metals Non-metals have only ONE choice: Will gain enough e - to make 8 valence e -.
12
METALLOIDS Have properties of BOTH metals & non- metals. 1.Treat like a “p” block metal (lose e - ) 2.Treat like a non-metal (gain e - )
13
III. Periodic Trends Anything that influences the valence electrons will affect the chemistry of the element. 1.Nuclear Charge 2.Energy Levels / # of core (inner) electrons.
14
1. Nuclear Charge (# of protons): A larger nuclear charge means a smaller outer level. b/c the higher positive charge of the nucleus pulls the valence e - inwards. 2. Energy Levels: Additional energy levels increase the distance between the nucleus and the valence e - Thus…the atom has more volume and a bigger radius.
15
3. Number of Core (inner) Electrons: More core electrons means a larger valence shell (aka atomic radius). Core e - repel the valence e - and push them farther away from the nucleus.
16
NUCLEAR CHARGE The # of protons in the nucleus Increases from L to R, across a period. Increases from top to bottom, down a group.
17
ATOMIC RADIUS Distance from the nucleus to the valence electrons. DECREASES from L to R across a period due to increasing nuclear charge. INCREASES from top to bottom down a group b/c of increased number of E levels (shielding).
18
Ionization Energy E required to remove an e - from an atom. INCREASES L to R across a period b/c of increasing nuclear charge. DECREASES from top to bottom down a group b/c of increased number of E levels.
19
Electron Affinity Ability to attract an e - (to form a anion). INCREASES L to R across a period b/c of increasing nuclear charge. DECREASES down a group due to the increase in E levels. NOTE: Noble gasses have NO electron affinity!
20
Ionic Radius Dist. from the nucleus to the valence e - Cations: Ionic radius is smaller than atomic radius b/c the atom has lost e - (smaller cloud) Anions: Ionic radius is larger than atomic radius b/c the atom has gained e - (larger cloud)
21
Electronegativity Ability to attract an e - in a chem compound INCREASES L to R across a period b/c of increasing nuclear charge. DECREASES (or stays about the same) from top to bottom down a group due to the increase in E levels.
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.