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Ch. 3: “Atoms and the Periodic Table”
Section 3.1: “Atomic Structure”
Objectives
1. Explain Dalton’s atomic theory, and describe why it was more successful than Democritus’s theory.
2. State the charge, mass, and location of each part of an atom according to the modern model of the atom.
3. Compare and contrast Bohr’s model with the modern model of an atom.
Dalton’s Theory
1. Every element is made of tiny, unique particles called _________________________ that cannot be subdivided.
2. Atoms of the same element are exactly _________________________.
3. Atoms of different elements can join to form _________________________.
 Dalton’s theory was widely accepted because, unlike Democritus’s theory, there was evidence to
_________________________ it.
Parts of an Atom
 proton (p+) = a _________________________ charged subatomic particle in the _________________________
of an atom
(mass = 0.00000000000000000000000000167 kg) Rewrite mass in scientific notation: ____________________
 neutron (n◦) = a _________________________ subatomic particle in the _________________________ of an
atom
(mass = 0.00000000000000000000000000167 kg) Rewrite mass in scientific notation: ____________________
 nucleus = the _________________________ of an atom; made up of _________________________ and
_________________________
 electron (e-) = a tiny _________________________ charged subatomic particle moving around the
_________________________ of the nucleus
(mass = 0.000000000000000000000000000000911 kg) Rewrite mass in scientific notation: _________________
The Bohr Model vs the Modern Atomic Theory
 In both theories, _________________________ orbit the nucleus and each electron has an energy level associated
with its location. In _________________________ model of the atom, electrons were thought to orbit the
nucleus in set paths, much like planets orbiting the sun. In the _________________________, the region in an
atom where electrons are likely to be found is called an orbital. But, the exact location of an electron cannot be
determined according to this model.
Electron Configuration
 The _________________________ the energy level, the farther from the nucleus the electrons tend to be, and the
_________________________ energy they have.
 Rules for filling energy levels:
 The first electrons enter the K shell, up to a maximum of _____.
 The next electrons enter the L shell, up to a maximum of _____.
 The next electrons enter the M shell, up to a maximum of 18, but are stable with _____.
 Valence:
 Whichever shell is currently _________________________ is the valence shell, even if it only has one electron.
 Valence electrons are those electrons that an atom uses in forming a _________________________ with another
atom. Generally, these electrons are found in the _________________________ shell of an element.
 How many valence electrons are in the first 18 elements?