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NAME ___________________________________________________ DATE _________________________
Chapter 4: Atoms
4.1 Atomic Theory
Democritus (400 B.C.)
 Ancient Greece
 Theorized that matter could not be ________________________ ______________________, you had
to reach a ________________________ __________________
 Atomos:________________________or can’t be cut (becomes ________________)
 Since this was ancient Greece, ___________________________________________________________
John Dalton (1808)
 People were more _____________________________ of his atomic theory because he
had _______________________
 His theory:

all ______________________ is made of ________________ (small solid spheres)

all ____________ are indivisible and indestructible

atoms of the same ________________________ are exactly ___________________

atoms of ______________________ elements are _____________________

_____________________ are formed by joining ____________ or more __________________
 Dalton’s theory of atoms supported the _______________________________________________
 Law of Definite Proportions: A chemical _______________
is made up of the same ______________ of
_______________________.
 This means that elements _____________________ is
whole number ratios when they ___________

Water is always made up of 2 parts hydrogen to 1
part oxygen giving us ____________
 This is true for all chemical _______________________!
Sir J. J. Thomson (1897)
 Conducted experiments with ___________________________ that showed atoms could be
_________________________
 His experiments showed ________________________ charged particles that came from inside
atoms

These are _____________________!
 A ___________________________ has two metal plates at the end of a vacuum tube

Cathode, which has a ___________________ charge

Anode, which has a ____________________ charge
 When voltage is applied across the plates, a
glowing _____________ comes from the
________________ and strikes the anode
 Since it was a vacuum tube (a tube with all the air vacuumed out), he could see that the beam
came from the ____________________ end of the cathode
 Successfully separated negative particles but could not separate the ___________________ particle
 Proposed that _______________________ are spread throughout
the ______________ like blueberries in a muffin

Called the _______________________________________
Ernest Rutherford (1911)
 Discovered the _____________________ using the
________________________ experiments
 Fired ____________________ charged particles at a sheet of
___________________________

Most went through unaffected, some ____________________ away
 His experiments suggested that an atom’s ______________________ charge was concentrated at
the ____________________ of the atom

This is the _____________________!
 His atomic theory stated that ___________________ are scattered near the outside of the
___________ with mostly _____________________ between the
__________________ and the electrons
 Compared to the atom, the nucleus is very _________________,
like a marble on of a football field!
Niels Bohr (1913)
 Proposed that ______________________ are arranged in circular
energy levels around the nucleus

Like planets orbiting the sun
 When electrons gain energy, they “____________” from a lower level to a higher, a loss of energy,
causes it to “_________” from a higher level to a lower
Erwin Schrodinger (1926) & James Chadwick (1932)
 His model does not define the exact path of an
__________________, but predicts its ______________________
 This model shows the ___________________ surrounded by an
electron “_________________”
 Chadwick discovered the ___________________, which has no
__________________________________, and the same mass as
the _________________
Modern Atomic Theory
 Today we know that atoms have

A ___________________ with

_____________________ and _____________________

And

______________________ that ____________ the nucleus like
_________________________________
4.2 Atomic Structure
Subatomic Particles
 Subatomic: lower (or smaller) than an atom
 Protons and electrons have an electrical charge

Protons: _______________________________

Neutrons: _______________________________

Electrons: _______________________________
Mass and Volume
 The ____________________ makes up ___________% of the mass
of the atom.
 However, the nucleus is 1/100,000 of the ____________________
of an atom.

The volume is determined by the ____________________
________________.
 Since subatomic particles are so small they cannot be measured
in ________________
 They are measured in atomic mass units or __________
 1 amu = 1.61x10-24 g
 1 g is about the mass of a paper clip!
Electrons
 Fill _____________________________________ around the nucleus
 Each _________________ only holds so many electrons
 Valence Electrons: ___________________________
____________________________________________
Atomic Number
 Atomic Number: number of ______________________ found in the
__________________
 The # of _____________________ in an ____________ is unique to each ____________________ and
is how we _________________________ an element – it ______________________________
 In a ___________________ atom, the number of ___________________ will equal the number of
_________________________ – meaning there will be NO overall ___________________ on the
atom
Atomic Mass
 Atomic Mass: ______________________________________________
__________________________________________________________
 Mass Number: _____________________________________________
__________________________________________________________

subtract _________________________ from ___________________________ to find number of
_______________________
 The number of neutrons in an atom can change, which means the atomic mass can change!
Isotopes
 Isotope: ______________ of the _____________ element with a _____________________ number of
__________________, and therefore different ____________________
 Normally 1-2 _______________________________________ for an element, and the atomic mass of
the ___________________________________ isotope is listed in your periodic table
 All others are _________________ (they fall apart) through _______________________ decay
Representing Isotopes
 Isotopes have the SAME ____________________ and ___________________ properties.
 Isotopes can be represented in a number of ways called isotope _______________________
 Element symbol or name with atomic mass
 Element symbol with atomic number and
atomic mass