Atomic Structure and Properties

Atomic Structure and Properties

What is Chemistry?

• Chemistry is the study of matter, its properties, and the changes that matter undergoes. 

• Put simply, it is the study of matter and its behavior.

Introduction to Matter

• Matter is the physical material of the universe; it is anything that has mass and occupies space.

• Mass describes the amount of matter.

• Volume describes how much space matter occupies.

Matter Continued..

• The matter we observe daily, has varying characteristics and properties. These properties help to distinguish one type of matter from another.

• Countless experiments have shown that all matter is comprised of a combination of only about 100 substances called elements.

• Each element has a unique atomic structure.

Matter and Atoms

• All matter is made up of extremely small building blocks called atoms.

• atoms are composed of protons, neutrons, and electrons.

• Protons are positively charged. (located in an atom's nucleus)

• Neutrons are neutral or not charged. (located in an atom's nucleus)

• Electrons are negatively charged (located outside an atom's nucleus)

Atoms Continued..

• Each element is composed of a unique type of atom.

• The properties of matter are related to both the types of atoms the matter contains (composition) and the physical arrangement of the atoms (structure).

• Several atoms can be joined together to create molecules.

• Molecules are two or more atoms that are joined in a specific arrangement.

Atoms verses Molecules

• Carbon is an element. The element carbon is only composed of carbon atoms.

• Whereas, carbon dioxide is a molecule. Carbon dioxide is composed of both carbon and oxygen atoms.

Classifications of Matter

• Matter is typically characterized by:

• (1) its physical state (gas, liquid, or solid)

• (2) its composition (whether it is an element, a compound, or a mixture)

States of Matter

• A sample of matter can be a gas, a liquid, or a solid. These three forms, called the states of matter, differ in some of their observable properties.

• A gas (also known as vapor) has no fixed volume or shape; rather, it uniformly fills its container. A gas can be compressed to occupy a smaller volume, or it can expand to occupy a larger one.

States of Matter Continued..

• A liquid has a distinct volume independent of its container, assumes the shape of the portion of the container it occupies, and is not compressible to any appreciable extent.

• A solid has both a definite shape and a definite volume and is not compressible to any appreciable extent.

Phase Change

• Matter will be in either a solid, liquid, or gas form depending on how much kinetic energy the particles have.

• The more energy the particles have the more space will be between the particles, the particles will move at high speeds, and the particles will collide more often.

• Changing the temperature and/or pressure of the particles can cause the matter to change from a solid, to a liquid, to a gas (or gas --> liquid --> solid)

• When matter changes from one state to another, this is called a phase change.

Pure Substances

• A pure substance (usually referred to simply as a substance) is matter that has distinct properties and a composition that does not vary from sample to sample.

• Water and table salt (sodium chloride) are examples of pure substances.

Elements and Compounds

• Elements are substances that cannot be decomposed into simpler substances. On the molecular level, each element is composed of only one kind of atom.

• Compounds are substances composed of two or more elements; they contain two or more kinds of atoms. Water, for example, is a compound composed of two elements: hydrogen and oxygen.