Atomic Structure Defining the Atom
Defining the AtomEssential Question How did the concept of the atom move from philosophy to science?
Defining the Atom • An is the smallest particle of an that retains its identity in a .
Philosophy or Science? • believed that matter consisted of tiny, indivisible, unchangeable particles called . • Until recent centuries the existence of the atom was a question rather than a one.
Philosophy to Science • Greater in allowed for experiments which indicated the existence of atoms. • Law of Conservation of , Law of Proportions, and Law of Proportions were clues to the existence of atoms.
Dalton’s Atomic Theory • 1) All are composed of tiny indivisible particles called . • 2) Atoms of one element are . The atoms of one are different from those of any other .
Dalton’s Theory (cont.) • 3) Atoms of different elements can mix together, or can chemically combine in simple whole-number ratios to form . • 4) occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Sizing Up the Atom • A copper penny contains about 2.4 x 1022 atoms. • Earth’s population measures about 6 x 109 people. • There are about 4 x 1012 times as many atoms in a penny as people on the earth.
Sizing Up the Atom • A line of 100,000,000 copper atoms side by side would be only 1 cm long.
Sizing Up the Atom • Sizes of atoms are expressed in (trillionths of a meter). • 1 cm is the same fractional part of 600 miles as 100 is of 1 cm!
Sizing Up the Atom • Dry air contains 0.002% Neon. • Yet there are about 5 x 1017 atoms of Neon in every breath you inhale! • That’s 500,000,000,000,000,000 atoms!
Sizing Up the Atom • In Summary: • Atoms are itty-bitty.
Atomic Structure Structure of the Nuclear Atom
Structure of the Nuclear AtomEssential Question What are the principle sub-atomic particles and what part do they play in the structure of the ?
The Structure of the Nuclear Atom • Atoms are known to be . • Sub-atomic particles include neutrinos, quarks, baryons, hadrons, fermions, bosons, mesons, leptons, photons, gravitons, gluons, , and . • Not to mention Nissans, futons and croutons.
The Structure of the Nuclear Atom We will be most concerned with protons, neutrons and electrons.
Subatomic ParticlesThe • Discovered by • charged particles • Relative charge = 1– • Symbol = e– • 1 / 1840 the mass of a proton • Reside of the nucleus
Subatomic ParticlesThe • Discovered by • charged particles • Relative charge = 1+ • Symbol = p+ • Mass of 1 atomic mass unit ()
Subatomic ParticlesThe • Discovered by • charged particles • Relative charge = 0 • Symbol = n0 • Mass of 1 atomic mass unit (amu)
The Atomic Nucleus • Discovered by (Gold Foil Experiment) • The tiny central core of an atom • Composed of and
The Atomic Nucleus • The is highly compacted and extremely dense. • of the mass of atoms is in the . • Nuclei have a of about 2 x 108 metric tons / cm3 !
Atomic Structure Distinguishing Among Atoms
Distinguishing Among AtomsEssential Question What part do protons, neutrons and electrons play in the and of atoms?
Atomic Number • The number of determines the identity of the element. • The number of protons is indicated by the .
Mass Number • The indicates the number of protons AND neutrons in the nucleus. • How do you find the number of from the mass number of a given element?
Isotopes • Isotopes are atoms of that have the same number of (the same element) but have different numbers of . • They, therefore, have mass numbers and different masses.
Atomic Mass • of atoms are incredibly small and impractical to express in grams • It is more practical to compare the of to a different standard.
Atomic Mass Unit • An AMU (atomic mass unit) is defined as 1/12 the mass of a atom. • Since the Carbon-12 atom is made up of 6 and 6 , an AMU is approximately equal to the mass of one proton or one neutron.
Atomic Mass • An element’s atomic mass is a average mass of all the atoms in a naturally occurring sample of the element. • To calculate atomic mass, the mass of each isotope by its percent abundance (expressed as a decimal) and add the products.