Download Chapter Two Section Two - Atomic structure Name: Dalton`s Atomic

Chapter Two Section Two - Atomic structure
Name: ________________________________
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Dalton’s Atomic Theory: Mid 1800s led to first changes
1. Atoms are divisible into even smaller particles
 These smaller particles are called __________________ PARTICLES
_____________, _____________, and _____________,
2. A given element can have atoms with different masses
 Scientists now know that all atoms of a given element do not necessarily have the same
mass.
 In nature, most elements consist of various Isotopes, atoms with the same # of protons but
a different # of neutrons.
Important Concepts that stayed true:
3. All matter is composed of atoms
4. Atoms of any one element differ in properties from atoms of another element
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A. Subatomic particles
1. Electrons
 Subatomic particle
 _____________ electric charge
 Found in energy shells _____________ the nucleus.
 Discovered using Cathode Rays by _____________________
Proposed that an atom’s electrons were embedded in a positively charged ball of matter
His model of an atom was named the __________________________
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Nucleus Discovery
 Ernest Rutherford performed the ___________________ experiment, which disproved the
plum-pudding model of the atom.
 _________________ found that most of the ________ particles shot at the foil passed straight
through the foil. But very few were deflected, in some cases backward.
 Only a very concentrated positive charge in a tiny space within the _______ atom could possibly
repel the fast-moving particles
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Nucleus
 The _____________ is the dense, central portion of the atom
 Made up of _____________ and _____________
 All the positive charge, nearly all the mass, but only a small fraction of the volume of the atom.
2. Protons
 Subatomic Particle
 _____________ electric charge
 Found in the nucleus
 Number of protons of the nucleus is the _______________________
3. Neutrons
 Subatomic Particle
 _________ electric charge
 Found in the nucleus
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Chapter Two Section Two - Atomic structure
Name: ________________________________
Coulomb’s Law states that the _________ two charges are, the _____________ the force between them
 Protons form a ___________ nuclei despite their repulsive force (+/+)
 Neutrons can add attractive forces, and stabilize the nucleus
 All atoms that have more than _______ proton also have _____________
B.
1.



Atomic Number & Mass
Atomic number (A#)
The number of ___________ in the nucleus of an atom
The ________ for all atoms of an element
Because each element has a unique number of protons in its atoms, no two elements have the same
atomic number.
 Always _________ numbers
EXAMPLE 1: The atomic number of Hydrogen is 1 because the nucleus of each H atom has 1 proton.
EXAMPLE 2: The atomic number of Oxygen is 8.
EXAMPLE 3: The atomic number of C is _________
In a NEUTRAL atom:
 The atomic number also reveals the number of _____________ in an atom of an element.
Atomic number = # of electrons
# of electrons = # of protons
Atomic number = # of protons
What is the atomic # and number of protons for the following elements?
1. H ___, ___
3. Li ___, ___
5. Sodium ___, ___
2. He ___, ___
4. Neon ___, ___
6. Magnesium ___, ___
Mass number (M#)
 The number of particles of the _____________
 The sum of the _____________ and _____________ in the nucleus of an atom.
 Round Mass to __________ number
 Unlike the Atomic Number (A#), the Mass Number can vary among atoms of a single element.
o Isotopes: Same element with the same number of Protons and different number of Neutrons
You can calculate the number of _____________ in an atom:
 Subtract the Atomic Number (#of protons) from the Mass Number (#of protons + neutrons)
 Mass Number – Atomic Number = Number of Neutrons
 M#-A# = # Neutrons
Example: A particular atom of Neon has a M# of 20.
Because the Atomic Number for an atom of Neon is 10, neon has 10 protons.
number of protons and neutrons (mass number) =
 number of protons (atomic number) =
number of neutrons =
20
- 10
10
The Neon atom has 10 Protons, 10 Electrons, and 10 Neutrons. The Mass Number is 20.
Mass number
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