Chemistry
John Newlands (1864)
-Noticed that the elements showed repeating properties when arranged by atomic mass. -Every 8th element, patterns repeated. He named it the Law of Octaves.
beta particle amu
0 amu
gramma ray amu
0 amu
John Dobereiner (1829)
(triads) arrange element into similar groups
Radioistopes
An unstable isotope This happens when the ratio of protons to neutrons in the nucleus is not ideal and causes instability.
proton importance
Determine the element adds mass
Electron importance
Determine the ion
mendeleev
First orderly arrangement of know elements left blank spaces for elements not yet discovered
protons
Positively charged particles
half-life
The time it takes for one half of a radioactive sample to decay
Henry Moseley (1913)
arranged the elements in the periodic table according to atomic numbers
halogens
most reactive nonmetals
alpha particle amu
4 amu
Alpha particle
A helium nucleus that can be blocked by paper or clothing. High energy nucleus. Charge 2+. paper
isotope
Atoms of the same element that have different numbers of neutrons
Nonmetals
Brittle, poor conductors, can be solid, liquid
neutron importance
Determine the isotope adds mass
chronological order of scientists contributing to the modern periodic table?
Lavoisier, Dobereiner, Newlands, Mendeleev, and Moseley
Metals
Malleable, ductile, Conduct electricity and heat well, mostly solids
semimetals
Properties of both metals and nonmetals
stability
The nucleus of an atom can change because it is trying to find stability
Radiation
The ray and particles emitted from a radioisotope or nucleus reaction.
radioactivity
When a nucleus breaks down into a different nucleus to become stable
Radioactive decay
When an unstable nucleus releases radiation and changes the original nucleus to a different element.
nuclear chemistry
When the nucleus (protons or neutron) of an atom changes.
One of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. Which property fits this description?
atomic mass
Transition metals
form colored compounds, good conductors of electricity
gamma rays
high energy electromagnetic radiation that can only be shielded with lead or several feet of lead. High energy electromagnetic radiation. 0 charge,
beta particle
high energy electron. 0 amu. wood or alumimun foil
Noble gases
lowest chemical reactivity, used in lighting
Alkali metals
most reactive,soft, oxidize quickly
Alkaline earth metals
not as reactive as alkali metals, brittle, shiny
Lavoisier
organized elements into four groups based on properties
inner radioactive metals
radioactive,used in nuclear power plants
