Chapter 17 Sec 1-4 Structure of the Atom

Elements Any material made up of only one type of atom is classified as an element. Any material made up of only one type of atom is classified as an element. Example – Pure gold contains only gold atoms Example – Pure gold contains only gold atoms Example – Nitrogen gas contains only nitrogen atoms Example – Nitrogen gas contains only nitrogen atoms All the elements are listed on a chart called the periodic table. All the elements are listed on a chart called the periodic table.

Scientific Shortcuts! Do you have a nickname? Do you have a nickname? What about abbreviations for the names of states or classes? What about abbreviations for the names of states or classes? EX: PS – Physical Science IL – Illinois EX: PS – Physical Science IL – Illinois Scientists do this too – especially in CHEMISTRY!

Chemistry Shortcuts! Elements are abbreviated with certain atomic symbols. Elements are abbreviated with certain atomic symbols. Many of these symbols come from Latin roots. Many of these symbols come from Latin roots. Elements are named after people, places, or properties. Elements are named after people, places, or properties. EX: H for Hydrogen He for Helium EX: H for Hydrogen He for Helium O for Oxygen Fe for Iron

Hydrogen Hydrogen was the first element to exist in the universe. Hydrogen was the first element to exist in the universe. It is the most common element – makes up more than 90% of all atoms. It is the most common element – makes up more than 90% of all atoms. Hydrogen is very light and has a simple structure. Hydrogen is very light and has a simple structure.

Size of an Atom Atoms are so small they can’t be seen with visible light. Atoms are so small they can’t be seen with visible light. We could stack microscope upon microscope and never be able to “see” an atom. We could stack microscope upon microscope and never be able to “see” an atom. Photographs of atoms are obtained with a scanning tunneling microscope. Photographs of atoms are obtained with a scanning tunneling microscope. This is a non-light imaging device that bypasses light and optics. This is a non-light imaging device that bypasses light and optics.

Atomic Components Remember Your Charges!! Protons and Neutrons are found in the nucleus of the atom Protons and Neutrons are found in the nucleus of the atom Nucleus is the positive center of the atom Nucleus is the positive center of the atom Electrons are circling around the outside of the nucleus. Electrons are circling around the outside of the nucleus.

Atomic Nucleus The atomic nucleus contains protons and neutrons. The atomic nucleus contains protons and neutrons. It makes up most of the mass of the atom, even though it is extremely small. It makes up most of the mass of the atom, even though it is extremely small. Electrons move around the nucleus. Electrons move around the nucleus. Most of the rest of the atom is empty space. Most of the rest of the atom is empty space.

Parts of the Atom

Subatomic Particle ParticleChargeSymbolMass Compared to an Electron Location Proton+1p+p+ 1836Nucleus Neutron0n0n0 1841Nucleus Electrone-e- 1Electron Cloud

Let’s get on with the Chemistry! ATOMIC NUMBER=# of protons in nucleus of atom ATOMIC NUMBER=# of protons in nucleus of atom Always whole numbers! Always whole numbers! Each atomic number is unique to a particular element! Each atomic number is unique to a particular element! Ex: All atoms with the atomic number 8 are oxygen atoms, all oxygen atoms have the atomic number 8!

Mass Number MASS NUMBER = total # of particles in the nucleus MASS NUMBER = total # of particles in the nucleus MASS NUMBER = total number of protons and neutrons MASS NUMBER = total number of protons and neutrons Ex: Boron has mass number of 11 and atomic number of 5. So it has 5 protons and 6 neutrons.

Isotopes ISOTOPES=atoms of the same element with different numbers of neutrons. ISOTOPES=atoms of the same element with different numbers of neutrons. A majority of elements exist as isotopes. A majority of elements exist as isotopes. Ex: Helium 4 Neutrons 5 Neutrons

Isotope Symbols Fe The superscript is the atomic mass. The subscript is the atomic number. Atomic Symbol Mass Number Atomic Number

Atomic Mass The total mass of an atom is the atomic mass. The total mass of an atom is the atomic mass. This is an average mass! It’s the average mass of all its various isotopes! This is an average mass! It’s the average mass of all its various isotopes! This is the mass shown on the periodic table. This is the mass shown on the periodic table. Elements have different masses! Elements have different masses!

ATOMIC NUMBER ATOMIC MASS

And they all lived happily ever after in Chemistryland!