Download Chemistry Name_______________________ Chapter 4

Chemistry
Chapter 4
Name_______________________
Hour__________Date__________
Chapter 4.1 –
Early Ideas About Matter 1. What did many Greek philosophers
believe matter was composed of?
Earth, fire, water, etc
2. What did Democritus (460-370 B.C.)
believe about matter? And about atoms?
not infinitely divisible. Made of atoms that
are not created, destroyed, or divided
3. What was Aristotle’s (384-322 B.C.)
belief on atoms?
Democritus believed these atoms could
move through empty space. Aristotle did
not believe in empty space
4. Explain Dalton’s (1766-1844)
Atomic Theory. Use Table 4.2 on p. 104.
1) All matter is made of atoms. Atoms are
indivisible and indestructible.
2) All atoms of a given element are identical
in mass and properties and different from
those of other atoms
3) Compounds are formed by a combination
of two or more different kinds of atoms.
4) A chemical reaction is a rearrangement
of atoms.
5. How does Dalton’s atomic theory explain
the law of conservation of mass?
If atoms cannot be destroyed then mass
can’t change during rxns
Chapter 4.2 – Defining the Atom
1. Define atom.
The smallest particle of an element that
retains the chemical identity of that element
2. What instrument is used to view
individual atoms and how does this
instrument work?
scanning, tunneling microscope (STM)
an electronic recording of the interactions
between a point moved over the surface of
atoms
3. The instrument allows scientists to do
what with the atoms? (Nanotechnology, p.
107)
move individual atoms around to make
shapes
4. What is a cathode-ray tube (Figure 4.6)
and what has it allowed researchers to
study?
glass tube with metal electrodes at each
end and then evacuated.
find particles leaving the cathode.
determine electron charge:mass
5. The accidental discovery of the cathode
ray from Sir William Crookes led to the
invention of television. Explain briefly
Crookes’ observations and thus his
discovery of the cathode ray.
light emitted when room darkened.
Something caused this light when it reacted
with the ZnS coated electrode
6. Define electrons.
negatively charged particles with no mass
that orbit atoms
7. How did English physicist J. J. Thomson
(1856-1940) determine the charge-tomass ratio of the charged particle/electron?
by determining the deflection of the
electron due to the magnitude of the fields
of magnetic and electric energy
8. Dalton’s atomic theory was proven false
by Thomson’s significant finding. Explain
his conclusion (p.109).
this particle with such a small mass meant
there were things present smaller than an
atom. (atoms are divisible)
9. American physicist Robert Millikan
(1868-1953) developed the oil-drop
apparatus to determine the charge of an
electron. A single electron carries what
charge?
1.602 x 10-19 coulombs. (-1)
10. How did Millikan control the rate of a
droplet’s fall?
changing the magnitude of the electric
charge
11. How did he calculate the mass of an
electron (p. 109)?
Knowing the charge and Thomson’s charge
to mass ratio
12. What explanation does Thomson’s plum
pudding model give about the charge of the
atom?
the charge is neutral and distributed about
the mass of the atom.
13. What was the purpose of the 1911
experiment conducted by Ernest
Rutherford’s (1871-1937) and his
colleagues (p. 111)?
To substantiate Thomson’s model of the
atom. (see if matter is evenly distributed in
atom)
14. Reading Rutherford’s experiment, how
did they determine if the atoms in the gold
foil deflected the alpha particles?
they didn’t pass straight through the foil
(they were deflected)
15. What were the results of the
experiment?
most passed straight through, some
deflected a little and some bounced almost
straight back.
16. Rutherford concluded that the plum
pudding model was incorrect. Explain his
nuclear model (Figure 4.13 ).
small dense center= nucleus.
electrons therefore must be around it
17. What caused the deflections?
the massive (comparatively) nucleus
18. Rutherford’s nuclear model introduced
the concept of the NUCLEUS which
contained positively charged PROTONS.
Rutherford’s coworker, physicist Chadwick
(1891-1974) showed that the nucleus also
contained neutral particles called
NEUTRONS. Define the terms proton,
neutron, and electron, include the
symbols.
(a) Proton pos charged 1 amu in nucleus,
p+
(b) Neutron neutral charge, 1amu in
nucleus, no
(c) Electron negative charge 0 amu orbit
nucleus, e-
19. Draw Rutherford’s model of the
atom114)
label each part.
Chapter 4.3 – How Atoms Differ
1. What identifies the atom of a particular
element?
atomic number
2. What is the atomic number?
number of protons in nucleus
3. Because atoms are neutral, the atomic
number can also determine what two things
about the atom?
proton and electron number
4. Define the term ISOTOPE.
atoms with same atomic number but
different mass. ( same p+ different no)
5. How do the mass of Isotopes vary as the
neutron number changes
neutrons increase, atomic mass increases
6. How are isotopes of each element
identified?
by mass number
7. How do you determine mass number?
write an equation that illustrates this
p+ + no
8. Define one atomic mass unit (amu).
mass of proton (1/12 of carbon nucleus)
9. Define ATOMIC MASS
weighted average of all naturally occurring
isotopes of the element
atomic mass= average of isotopes
mass # = wt of 1 atom
10. How does atomic mass differ from mass
number then?