Transcript Document
How are atoms studied? • Atoms are the building blocks of matter • Atoms are too small in size to study easily • Size of Earth : soda can = soda can : atom Who studied the atom? • Studied by many scientists for centuries – – – – – Democritus (400 BC) – phrase “atomos” Rutherford (1911) – nucleus (gold foil expt) Moseley (1913) – X-rays to find atomic # *Bohr (1913) – planetary model of the atom *Schrödinger (1923) – electron cloud model I’m an electron! I’m a proton! I’m a neutron! I was walking along and I saw these two. I was telling jokes to the neutron. The proton and I were having fun. They looked so happy there together. I was p o s i t i v e l y charged! I couldn’t have amassed more happiness. The proton looked happy, so I wandered closer. I could see the electron coming near. The who? Huh? They were HUGE next to me! The electron was so cute! Like a speck of dust, or something… I didn’t want to seem obvious, so I kept walking. Around and around the electron goes. Hey electron, you’re making the proton dizzy. The proton seems so happy with the neutron. I’m having fun, but I still notice the electron. It won’t bother me if the electron hangs around. I guess I’ll just wander around out here. I’m happy hanging out here. The center is cool, but sometimes it can be a “Bohr”. Electrons circle around the nucleus of an atom. Protons are a main part of the nucleus of an atom. Neutrons also hang out in the nucleus of an atom. Electrons have a negative charge. Protons have a positive charge. + Neutrons have no charge. 0 Electrons are little and have a mass of almost zero. Protons are big and have a mass of one. Neutrons are also big and have a mass of one. What is the structure of an atom? • Nucleus – center of the atom – Home of Protons and Neutrons – Proton • Has a positive (+) charge • Has a relative mass of 1 • Determines the atomic number • Found inside the nucleus What is the structure of an atom? – Neutron • Has no (0) charge • Has a relative mass of 1 • Determines the isotope – Isotopes are two of the same element with different masses • Found inside the nucleus What is the structure of an atom? • Electron – Has a negative (-) charge – Has a relative mass of 0 (zero) – Determines the ion – Found outside the nucleus • Bohr model – electrons are in specific energy levels • Electron cloud model – electrons are in a random cloud What is the structure of an atom? Bohr Model Schrödinger Model “Planetary Model” “Electron Cloud Model” How are P, N, e related? • # protons = atomic number • # electrons = # protons in a neutral atom • # protons + # neutrons = atomic mass What is a chemical symbol? • Chemical symbol tells us what atom it is • Always a CAPITAL LETTER, sometimes followed by a lower case letter • Ex: Oxygen O Nitrogen N Sodium Na • *Cobalt – Co *Carbon Monoxide – CO • (Co is an element, CO is a compound)