Chemistry

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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


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