Dmitri Mendeleev
Russian Chemist, used atomic mass and similar chemical properties to arrange elements into groups (families). Constructed first table in 1869. Left blank spaces and predicted the existence of three elements whose properties ended up being very similar.
Henry Mosely
English scientist, modified the periodic table in 1913. He found that elements relate better when arranged by atomic number (how they are arranged today).
Periodic Law
When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.
Periodic Table
Used to understand and predict properties of elements. Has 18 groups and 7 periods.
118
How many elements are on the modern day periodic table?
Group
18 of them. Elements have similar physical and chemical properties
Period
7 of them. The properties of elements change as you move across them from element to element. Pattern of properties repeats as you move from one to the next.
Metal
Good conductors of heat and electricity, high luster when clean, ductile, malleable, and solid at room temp (except Mercury).
Nonmetal
Nonmetallic, non-lustrous, poor conductors of heat and electricity. Some are gas (oxygen, chlorine, fluorine, nitrogen), some are brittle solids (sulfur, carbon, selenium, iodine), and bromine is a liquid at a room temp.
Metalloid
Properties are intermediate between those of metals and nonmetals. Form a step line. They are semiconductors and all solids. Elements: Boron, silicon, germanium, arsenic, antimony, and tellurium (sometimes astatine and polonium).
Alkali Metal
Other name for group 1 elements
Alkaline Earth Metals
Other name for group 2 elements
Halogens
Other name for group 17 elements
Noble Gases
Other name for group 18 elements
Transition metals
Located in groups 3-12 and period 4-7
Inner Transition Metals
Pulled out rows of the periodic table. Include Lanthanides and Actinides. Also called Rare Earth Metals.
Atomic Radius
1/2 the distance between the nuclei of two like atoms in a diatomic molecule
Trends in Atomic Size
Increases as you move down a group because electrons are added to higher energy levels. Decreases as you move left to right across a period because of an increase of positive charges between the nucleus and electrons (pulls in, makes atom smaller). Francium largest, Helium smallest.
Ion
Atom or group of bonded atoms that has a charge.
Ionization Energy
Energy required to remove an electron from atom
Trends in Ionization Energy
Decreases as you move down a group because the size of atoms increase and electrons are farther away from the nucleus making it easier to remove them. Increases from left to right across a period because there is a greater attraction of nucleus for the electron. Helium largest, Francium smallest.
Electron Affinity
Energy charge that occurs when an electron is gained by a neutral atom.
Trends in Electron Affinity
Decreases as you move down a group. Increases as you move left to right across a period because the closer to a full sublevel, the higher it is. Fluorine largest, Francium smallest. Groups 2 & 18 have zero.
Ionic radius
The size of a cation or anion. Cation is smaller and a anion is larger.
Cation
Positively charged ion, lost electrons, size decreases (half the radius of neutral)
Anion
Negatively charged ion, lost electrons, size decreases (half the radius)
Trends in Ionic Size
Increase as you go down a group. Decreases from left to right until Group 15. Group 15 elements increase (between metals and nonmetals) and then decrease until Group 18.
Electronegativity
The measure of the ability of an atom in a chemical compound to attract electrons from another atom.
Trends in Electronegativity
Decreases as you move down a group. Increases as you move left to right across a period. Noble Gases are not included because they are not attractive. Fluorine largest because it attracts electrons, Francium smallest because it easily loses an electron.
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