Atomic Structure Timeline

* Protons and electrons have equal and opposite electrical charges. Protons are positively charged, and electrons are negatively charged.

In this experiment, you will have a chance to test the hypothesis that Ernest Rutherford used when determining the size of the nucleus. In his "gold foil experiment," Rutherford shot alpha particles at gold atoms. Once he realized that the alpha particles were hitting a concentrated positive mass, he developed the nuclear model of the atom. Next, he set out to determine the relative size of the nucleus compared to the rest of the atom. He reasoned that the smaller the nucleus, the less likely it was to be hit by an alpha particle. This led to a simple comparative ratio:

In the year 400 B.C, the first atomic structure was made. It was thought that everything could be broken down into very small particles. These small particles are atoms, which it is what atomic structure is all about. Atomic structures are visual demonstrations used to help understand how an atom looks like on the interior in the inside and what it consists of. Over the years, atomic structures have greatly improved and are still doing so. However, the first atomic structure had a great impact on science and on other observations made about atoms.

The identity of each element is defined by the number of protons in its nucleus

The Ancient Greeks were the firsts to speculate on the composition of matter. They thought that it was possible that individual particles made up matter.

Protons, neutrons and electrons are different from one another; they have their properties and/or characteristics.

isotopes have the same chemical properties as their elements but different chemical properties. This is because isotopes of an element have the same number of electrons as an atom of that particular element. The electron arrangement is what affects chemical properties, and isotopes have the same electron arrangement , so they have the same chemical properties. However the have a different number of neutrons which changes the mass number. The mass number is what determines the physical properties , such as boiling point and

the old view of atoms as the basic building blocks of the material world and Newtonian physics

Every element is special because none are ever the same. Even an atoms isotope is different. Krypton’s atomic number is 36. Its atomic mass is 83.798 units. The number of protons in an element, which is also the atomic number, is 36. It also

Around 2,500 years ago, Democritus and his partner Leucippus were the first ones to develop the atomic theory in written history. Their theory proposed that every kind of matter was made up of tiny particles, which were named atomos, which means that it is indivisible. This meant that Democritus and Leucippus thought there were little particles of everything, but, the next breakthrough in atomic theory wasn’t made until the early 1800s with a french chemist by the name of Antoine Lavoisier, he was the one who came up with the idea of the law of the conservation of mass, which states that matter stays the same even when it changes shape or form. Then, James Dalton said that all matter was made up of atoms, which were indivisible, and unbreakable.

He stated that this was a mysterious force but never continued his research on it. Then in 460 B.C. there was a philosopher named Democritus. Democritus and his mentor Leocippus posed the question that if he broke bread into multiple pieces how many would breaks would it take until there was no more bread. He then was able to make a few theories being all matter was created of atoms and atoms are solid but not invisible. However, there was a man named Aristotle and many other philosophers who disagreed with Democritus and said matter was composed of four main elements. Earth, fire, air, and water. For example, a liquid was made of water and a stone was made of rock. Therefore, Democritus’s theory “ was rejected by Aristotle, one of the most influential philosophers of Ancient Greece; and the atomic theory was ignored for nearly 2,000 years.”(

Because the structure of the atoms has always puzzled scientists, the idea of the atom had changed throughout the history of Earth. Democritus had originally issued the idea of atoms. (Doc 1) He proposed that the materials could be broken down until the thing couldn’t be broken down anymore. (OI)

Scientists once thought that atoms were the main building blocks of matter. Research and experimentation led them to the discovery of protons, neutrons, and electrons. Satisfied with their discovery, they could not have possibly imagined anything smaller than a proton or a neutron, which is about 10-15 in diameter. The first idea for a smaller particle came in 1935 from Hideki Yukawa, who thought that there were smaller particles which could hold the neutrons and protons together in the nucleus (Chen 14). However, in 1964, Murray Gellmann and George Zweig independently postulated, then discovered, the quark, the smallest particle of matter that has yet been discovered. Simply postulating the quark did not fool other scientists, though, and

The nucleus is in the center of an atom and is made of neutrons and protons, the nucleus also acts like the control center of an atom. Isotopes have a different number of neutrons than protons. Every atom is a different element, they have properties that only one atom has and also have similar properties. These properties of elements

The Discovery of the Atom first came from the Greeks which made a theory “The idea that all matter is made up of tiny, indivisible particles, or atoms, is believed to have originated with the Greek philosopher Leucippus of Miletus and his student Democritus of Abdera in the 5th century B.C. (The word atom comes from the Greek word atomos, which means “indivisible.”)” (InfoPlease Atomic theory)