Week 2: How the elements are formed (part 2) Flashcards
Who originated the atom concept ?
Leucippus of Miletus,
Who helped refine and extend the atom concept in future years ?
Democritus
known as the “Laughing Philosopher”
Democritus
Who is the earliest known Greek philosopher ?
Thales of Miletus
Point #1
All matter is composed of atoms, which are bits of matter too small to be seen. These atoms CANNOT be further split into smaller portions.
Point #2
There is a void, which is empty space between atoms.
pure substance that cannot be separated into any other substances
element
there are how many naturally occurring elements ?
92
The smallest particle of an element that still has the properties of that element is what?
the atom
For about 2000 years, people accepted ____ idea that all matter is made up of just four elements: earth,air, water, and fire
Aristotle
Starting about ____ years ago, scientists began discovering all of the elements that are known today.
500
Why is gold considered to be valuable?
Because it was fairly rare and it is also a common means of paying for goods and services
Who owned the gold mines during the ancient Egyptian and Roman civilizations?
the gold mines were property of the state not an individual or group
What contributions to modern chemistry were made by the alchemists?
Early acids and bases were discovered aand it helped improve the study of metallurgy and the extraction of metal ores
electron:
A negatively charged particle that has a very small mass compared to the mass of other subatomic particles and surrounds the atom.
plum pudding model:
An experiment, led by J.J. Thomson, which proposed that the atom was comprised of negatively charged particles in a disperse field of positively charged particles.
radioactivity:
When certain substances emit charged particles.
gold foil experiment:
An experiment, led by Ernest Rutherford, which proposed that atoms consist of a small positively charged nucleus surrounded by negatively charged electrons.
proton:
A positively charged particle that has a relatively large mass compared to electrons. Protons can be found in the nucleus of the atom.
neutron:
An uncharged particle with a mass nearly equal to that of the proton. Neutrons can be found in the nucleus of the atom
the atom is comprised of three subatomic particles called
electrons, neutrons, and protons
Who discovered cathode rays, which later became known as electrons?
William Crookes
Crookes discovered these rays using an apparatus he developed called the Crookes tube or the _______
cathode ray tube
which were initially called cathode rays, are negatively charged and have a very small mass compared to the masses of other subatomic particles
electrons
Who discovered X-rays?
Wilhelm Conrad Roentgen
Who showed that cathode rays are deflected in a magnetic field and proposed that cathoderays are streams of negatively charged particles?
J. J. Thomson
This model described the atom as a disperse field of positive charge containing small negatively charged particles
Plum pudding model
Who proposed the plum-pudding model of the atom?
Thomson
In 1909, the magnitude of the charge carried by an electron was determined by who in an experiment known as the oil drop experiment?
Robert Millikan
In 1919, who discovered the presence of a positively charged nucleus with his famous gold foil experiment ?
Rutherford
In 1932, who discovered the neutron, a particle with a mass similar to that of the proton but without any electrical charge?
Chadwick
_____ are particles with a mass similar to that of the proton, but they have no electrical charge. they also reside in the nucleus
neutrons
The nucleus contains two types of subatomic particles:
protons and nuetrons
positively charged subatomic particle in a nucleus
protons
subatomic particle in a nucleus with no charge
neutrons
