chapter 4 development of the periodic table –mendeleev vs moseley mendeleev (mid 1800’s)...
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Chapter 4 • Development of the Periodic Table
– Mendeleev vs Moseley • Mendeleev (Mid 1800’s)
– Discovered a repeating pattern as he arranged elements by atomic mass. (Every seventh element had similar behavior, color, etc) – This is due to periodic properties (when things repeat regularly)
– Valence electrons gained or lost (outermost electrons in an atom responsible for behavior) repeated 1234321
– Left gaps for missing elements– Didn’t include noble gases (inert gases) because he
didn’t know they existed because they don’t react with things
Chapter 4
• Moseley (early 1900’s)– Fixed Mendeleev’s errors by adding in missing
elements– Added noble gases– Discovered elements atomic number and
arranged by this which fixed some misplacements
Chapter 4 Notes• Trends on Period Table
– Atomic Radius – Size of the atom, increases as you go down a group and decreases as you move across a period b/c the electrons are held more tightly by the nonmetals.
– Ionization Energy – Energy required to remove an electron to make the atom an ion. Increases as you move up and the right. Fluorine has highest, Francium is the lowest.
– Electron Affinity – Want for more electrons, follows the same trend as ionization energy.
Chapter 4 Notes
• Need to know the families of the periodic table– Alkali Metals (1)– Alkaline Earth Metals (2)– Transition Metals (3-12)– Boron Family (13)– Carbon Family (14)– Nitrogen Family (15)– Oxygen Family (16)– Halogens (17)– Noble Gases (18)
Chapter 4
• Active metals (Groups IA/1 and IIA/2)– Alkali metals (Group IA) included Lithium,
Sodium, Potassium, Rubidium, Cesium, and Francium.
• They are the most active metals on the table. They are close to noble gas status so they react quickly to get there.
• Soft metals that can be cut with a knife, rarely found in nature b/c they react with water violently.
• Only contain one valence electron (+1 Charge)
Chapter 4
• Alkaline Earth Metals (Group 2/IIA)– Contain Berylium, Magnesium, Calcium,
Strontium, Barium, and Radium– Metals that are often needed by the body for
health, used in medicines, also burn pretty easily (photography, flares, fireworks)
– 2 valence electrons – give them up to become stable (+2 charge)
– Not quite as reactive as group 1
Chapter 4
• Transition Metals (Group 3-12)– Metals that don’t fit into a particular family. – Excellent conductors, good for jewelry and
building materials due to high density and strength.
– Have 2 valence electrons so they tend to be a +2 charge however some give up more.
– Fairly stable metals!
Chapter 4
• Metals to Nonmetals (Groups IIIA/13 to Group VIA/16)
• Boron family (contains Boron, Aluminum, Gallium, Indium, Thallium)– Top behave more like non metals and as you go down
they become more metallic
– 3 valence electrons (+3 Charge)
– Good for alloys, more heat resistant, form oxides
Chapter 4
• Carbon Family (Group 14)– Contains – Carbon, Silicon, Germanium, Tin,
Lead– Again become more metallic as you move
down the column– Have 4 Valence electrons (+4 or –4 charge)– Most versitale group, many bonding sites,
Carbon most important in this group to us– Silicon good for computer chips
Chapter 4
• Nitrogen Family (Group 15)– Contains – Nitrogen, Phosphorus, Arsenic,
Antimony, Bismuth– Nonmetal at top to metal at bottom– 5 valence electrons (easier to gain 3 electrons
than lose 5 = -3 charge)– Somewhat reactive group, uses include
fertilizers, explosives, drugs and dyes
Chapter 4
• Oxygen Family (Group 16)– Contains – Oxygen, Sulfur, Selenium,
Tellurium, and Polonium– More reactive than group 15– Have 6 valence electrons (-2 charge)– Needed by body, used to make many
compounds, drugs, matches, gun powder, alloys.
Chapter 4
• Halogens (Halogen means salt forming) (Group 17)– Include elements Fluorine, Chlorine, Bromine,
Iodine, Astatine– Have 7 Valence electrons – Most reactive
Nonmetals (-1 charge)– Good for disinfectants, Diatomic elements
(Bond to themselves), Form salts
Chapter 4
• Noble Gases (Group 18)– Contain Helium, Neon, Argon, Krypton,
Xenon, Radon– Have a full valence shell (8 electrons) = Non
reactive (Inert)– Neon signs, balloons/blimps, cancer treatment,
photography
Chapter 4 Notes4 forces acting within an atom
* Electromagnetic force – Holds electrons to atom because of attraction of opposite charges
* Strong Force – between protons, keeps protons from repelling and breaking up nucleus
* Weak force – Radioactive decay, breaking of an atom over time
* Gravity – Attraction to mass
Chapter 4 NotesMoles, Mass, Molecules Conversions
- Based on Formula Mass (mass from periodic table for each element) compounds require us to add mass of each part to get total mass.- Example H2O
- Hydrogen has a mass of 1 and we have 2 of them so 1*2=2
- Oxygen has a mass of 16 and we have 1 of them so total mass = 2+16=18
Chapter 4 Notes
Formula mass is the mass found in one mole of a substance. It is based on Avegadro’s number (6.02*1023) Number of molecules in 1 mole.