17.1: STRUCTURE OF THE ATOM PS- 2.1 COMPARE THE SUBATOMIC PARTICLES OF AN ATOM WITH REGARD TO MASS, LOCATION, AND CHARGE, AND EXPLAIN HOW THESE PARTICLES AFFECT THE PROPERTIES OF ATOMS (IDENTITY, MASS, VOLUME, AND REACTIVITY)

SCIENTIFIC SHORTHAND Names of elements can be long and complicated, so scientists developed a “shorthand” method. Chemical symbols have either one capital letter or a capital letter plus one or two smaller letters.

SCIENTIFIC SHORTHAND For some elements, the symbol is the first letter of the element’s name. For others, the symbol is the first letter of the name plus another letter from it’s name. This system is used worldwide so everyone understands what the symbols mean.

ATOMIC COMPONENTS An element is matter that is composed of only one type of atom, which is the smallest piece of matter that still retains the property of the element. Atoms are composed of particles called protons, neutrons, and electrons.

ATOMIC COMPONENTS Protons and neutrons are found in a small, positively charged center of the atom called the nucleus. The nucleus is surrounded by a cloud containing electrons.

ATOMIC COMPONENTS Protons are particles with an electrical charge of +1 Electrons are particles with an electrical charge of -1 Neutrons are neutral particles that do not have any electrical charge.

ATOMIC COMPONENTS The nucleus is located in the center of an electron cloud. The electron cloud is the space where electrons are moving erratically in areas of space called energy levels. Energy levels are regions of space at increasing distances from the nucleus.

ATOMIC COMPONENTS Electrons with more energy occupy energy levels further from the nucleus.  There are a maximum number of electrons that can occupy each energy level and that number increases the further the energy level is from the nucleus

ATOMIC COMPONENTS The net charge of the nucleus is positive and equal to the number of protons. Protons and neutrons have about the same mass. The mass of an electron is much less than the mass of protons and neutrons

PARTICLE CHARGE There is an attractive force between electrons and protons. There is a repulsive force between electrons and electrons, and between protons and protons. Understand that atoms are neutrally charged because the number of electrons is the same as the number of protons.

QUARKS- EVEN SMALLER PARTICLES… Protons and Neutrons are made up of even smaller particles called quarks. Scientists have confirmed the existence of 6 different quarks.

QUARKS One configuration of quarks makes a proton. A different configuration of quarks makes a neutron.

MODELS Scientists use models to represent things that are difficult to visualize in your mind.

EARLY ATOMIC MODEL 1800s, John Dalton constructed the first model of the atom, which depicts the atom as a solid sphere. Changed since then.

1926 the Electron Cloud Model was adopted. An electron cloud is the area around the nucleus of an atom where its electrons are most likely found. ELECTRON CLOUD MODEL

Electron cloud is 100,000 times larger than the diameter of the nucleus. Every electron in the cloud is much smaller than a single proton. Since the electron’s mass is so small and it is moving so quickly around the nucleus, it is impossible to tell its exact location in an atom.

REVIEW What is the smallest piece of matter that still retains the property of the element?

REVIEW Atoms

REVIEW What particles are found in the nucleus of an atom?

REVIEW Protons and neutrons

REVIEW What is the name of the small particles that make up protons and neutrons?

REVIEW Quarks

REVIEW Where are the electrons of an atom found?

In the electron cloud orbiting the nucleus. (protons and neutrons)

QUICK RESEARCH Who is credited with discovering quarks? What is the name of the book that inspired him/her to name the discovery “quark”?