Adv. Chem Ch. 4: The Periodic Table

METALS LOSE ELECTRONS!

Law of Constant Composition

given compound always contains same proportions, by mass of the elements

Dalton’s Postulates

1) elements are made of tiny articles called atoms
2) all atoms in a given element are identical
3) atoms of a given element are different from those of any other element

4) atoms of 1 element can combine with others to form a compound

5) atoms are indivisible in chemical processes

J. J. Thomson

cathode-ray tube experiment; discovered electrons; hypothesized protons

William Thomson (Lord Kelvin

Plum Pudding Model (electrons scattered at random in the atom)

Ernest Rutherford

known for the gold foil experiment, discovered the nucleus

Rutherford and Chadwick

discovered the neutron

electrons

negative charge, small mass, outside the nucleus, changes the charge

protons

positive charge, relatively large mass, inside the nucleus, determines element/mass, changes the element when u change it

neutrons

no charge, relatively large mass, inside the nucleus, determines mass, forms isotopes when changed

isotope

same number of protons, different number of neutrons

periodic table

shows all of the known elements in the order of increasing atomic number

groups

elements in the same vertical columns and have similar chemical properties

periods

horizontal rows of elements

physical properties of metals

efficient conduction of heat and electricity, malleability, ductility, lustrous appearance

physical properties of nonmetals

many are diatomic (always found as a 2-atom molecule), can be gasses, solids, and liquids at room temperature

physical properties of metalloids

exhibit a mixture of metallic and non-metallic properties; good semiconductors

allotropes

different forms of the same element

ions

gaining or losing electrons

cations

lose electrons to form positive ions

anions

nonmetals tend to gain electrons to form negative ions; uses the suffix -ide