Chapter 3: Atoms: The essential building blocks Flashcards
Atomic theory
1) elements are made of tiny particles (atoms)
2) each atom in an element is unique
3) atoms are not changed but combine into a whole number ratios
4) atoms are unchanged in chemical reactions
alpha particles
composite particles consisting of two protons and two neutrons tightly bound together
Law of conservation of mass
matter is neither created nor destroyed in chemical reactions
-atoms are rearranged in chemical reactions
Isotopes:
atoms that have the same atomic number but a different mass number
-can also have the same amount of protons but different number of nuetrons
Atomic number
the number of protons in an atom
Mass number
the number of protons + the number of nuetrons
Atomic Mass
The atomic mass of an element is the weighted average of the atomic masses of the naturally occurring isotopes of that element.
Weighted Average
determined by multiplying the percent of natural abundance by the actual mass of the isotope then adding all the products together
Ions
atoms or groups of atoms that contain an overall charge
Cations
positively-charged ions
Anions
negatively-charged ions
plum pudding model
atoms are solid and the electrons are spread through a positive layout
Bohr Model
electrons orbit the nucleus
Scanning Tunneling Microscopy
visualize atoms on a metal surface, to manipulate atoms
Ernest Rutherford
surrounded the gold film with a material that glowed when particles struck it.
* expected the alpha particles to pass through the film and hit behind it but some small number of the particles deflected off the film, and back toward the alpha particle source!
-Conclusion: The atom is mostly empty space, with a dense nucleus at the center.
