Atomic Structure

What is Matter?

Objectives Explain the relationship between matter, atoms, and elements Distinguish between elements and compounds Describe molecules, and explain how they are formed Interpret and write some common chemical formulas Categorize materials as pure substances or mixtures

What is chemistry and matter? Chemistry: the scientific study of the composition, structure, and properties of matter and the changes that matter undergoes. Matter: anything that has mass and takes up space.

Element: a substance that cannot be separated or broken down into simpler substances by chemical means. Atom: the smallest unit of an element that maintains the properties of that element Compound: a substance made of atoms of two or more different elements that are chemically combined.

Molecule: the smallest unit of a substance that keeps all of the physical and chemical properties of that substance. –A compound is made of two or more different elements, but a molecule may be of the same elements or different elements.

Remember: some elements occur singly in nature –Ex) Neon The atoms of other elements combine to form polyatomic molecules –Ex) O 2 H 2 P 4

Molecules can be represented by: –Formula –Physical models Chemical formula- a combination of chemical symbols and numbers to represent a substance C 16 H 10 N 2 O 2 Indigo C 8 H 10 N 4 O 2 Caffeine

Objectives Explain Dalton’s atomic theory State the charge, mass, and location of each part of an atom according to the modern model of the atom

What are atoms? Atoms are tiny undit that determine the properties of all matter. John Dalton developed an atomic theory: He believed that atoms could not be divided, however we know today that they can be broken down further into smaller particles.

An atom is the smallest part of an element that still has the element’s properties An atom consists of subatomic particles: –Nucleus- an atom’s central region which is made up of protons and neutrons –Proton- a subatomic particle that has a positive charge and that is found in the nucleus of an atom –Neutron- a subatomic particle that has no charge and that is found in the nucleus of the atom –Electron- a subatomic particle that has a negative charge

Draw and label the atomic structure!!!

Unreacted atoms have no overall charge Example: Helium –Charge of two protons: +2 –Charge of two neutrons: 0 –Charge of two electrons: -2 –Total charge of a helium atom 0

Electrons An electron’s exact position can not be determined Electrons exist in energy levels Each energy level holds a certain number of electrons Electrons behave like waves

Electrons per energy level

The periodic table objectives: Relate the organization of the periodic table to the arrangement of electrons within an atom Explain why some atoms gain or lose electrons to form ions Determine how many protons, neutrons, and electrons, an atom has, given its atomic number and mass number

Refer to the periodic table assignment and atom chart Know the following terms: periodic law period group/family ion atomic number mass number isotope atomic mass unit average atomic mass