Chapter 17 Sections 1 and 2

Atomic Components Atom– smallest piece of matter that still retains the property of the element Nucleus—the small, positively charged core of an atom where the protons and neutrons reside Protons—positively charged particles Neutrons—neutrally charged particles Electrons—negatively charged particles

Quarks Small particles that make up protons and neutrons Scientists theorize that an arrangement of three quarks held together with the strong nuclear force produces a proton. Another arrangement of three would produce a neutron.

To find quarks, scientists accelerate charged particles to tremendous speeds and then force them to collide with protons. This causes the proton to break into smaller pieces known a quarks. Scientists use inference to identify the subatomic particles and to reveal information about each particle's inner structure.

Models There have been 5 accepted models of the atom. Dalton/ Democritus Thomson Rutherfod Bohr Electron Cloud

Dalton’s Model Dalton’s model was that of a solid sphere

Thomson’s Model Atoms contain small, negatively charted particles He said these electrons (pictured in blue) were evenly embedded throughout a positively charged sphere, much like chocolate chips in a ball of cookie dough.

Rutherford’s Model Almost all the mass of an atom—and all it’s positive charges—were concentrated in a central atomic nucleus surrounded by electrons.

Bohr’s Model Electrons traveled in fixed orbits around the atom’s nucleus.

Chadwick He didn’t create a new model just expanded what his teacher Rutherford did. He concluded that the nucleus contained positive protons and neutral neutrons. This worked with Bohr’s model.

Modern Model Electrons do NOT follow a fixed orbit, but tend to occur more frequently in certain areas around the nucleus at any given time

Atomic number and mass Atomic number is the number of protons in an atom. By looking at the atomic number you can figure out how many neutrons there are as well. Neutrons equal the protons unless it is an isotope An isotope is an atom that has a different number of neutrons.

Atomic mass or mass number is the sum of the number of protons and neutrons in the nucleus. IF you know the mass number you can calculate the number of neutrons the equation is: Number of neutrons = mass number – atomic number