Atomic structure
1. Give the scientist who is responsible for each model
__1. An indivisible sphere with uniform density
__2. A positively charged atom embedded with electrons
__3. A small, dense, positively core with most of the atom empty space
__4. A small, dense nucleus consisting of protons and neutrons with electrons in levels
outside the nucleus
1.
Dalton
2.
Thomson
3.
Rutherford
4.
Bohr (modern)
2. a. How will you describe an electron? Write three points.
b. Describe sub atomic particles?
Electron , proton , neutron
3. What three things did Rutherford observe in his gold foil experiment and what did
they tell him about the atom?
1. Most of the alpha particles pass straight through the atom. This told R that they hit
nothing. Most of the atom is empty space.
2. A few of the alpha particles (which have a positive charge) were deflected. This told R that
the alpha particles passed close to something with a positive charge. The nucleus is positive.
3. A very few alpha particles bounced straight back. This told R that the alpha particles his
something that is very massive and very small (very dense). His conclusion is that the atom
has a small, dense, positively charged core. We call this the nucleus. Most of the atom is
empty space.
4. Determine the number of electrons, protons and neutrons in the following
isotopes.
A 1633S-2
B
Lithium-7
16 p,18 e,17 n
3p,3 e and 4 n
5. Which of these contains the greatest number of electrons
Al
Al+3
Al -2
Al -3
6. Explain why 1224Mg and 1225Mg are classified as isotopes. How will you
calculate number of neutrons from given information
Isotopes are the same element because they have the same number of protons, but
they have different numbers of neutrons and therefore different atomic masses.
7. Lithium – 7 has an atomic number of 3 and an atomic mass of 7 because
A.
it has 3 protons and 7 neutrons
B.
it has 3 protons and 4 neutrons
C.
it has 7 protons and 3 neutrons
D.
it has 4 protons and 3 neutrons
8. Choose which pair below are isotopes of each other
A.
24
12 Mg
B.
24
12
C.
27
13 Al
D.
13
Mg
27
Al
25
12 Mg
24
13 Al
13
27
Si
24
12 Mg
9. Use this representation of an atom to tell the number of protons, neutrons and
electrons.
14 2+
6 C
A.
B.
C.
D.
6
6
6
6
protons,
protons,
protons,
protons,
14 neutrons, 6 electrons
14 neutrons, 4 electrons
14 neutrons, 8 electrons
8 neutrons, 4 electrons
10. When Mg becomes a cation it
A. loses 1 electron to have a +1 charge
B. loses 2 electrons to have a + 2 charge
C. gains 1 electron to have a -1 charge
D. gains 2 electrons to have a -2 charge
11. Tell if energy is absorbed or released when
A.
an electron leaps from a lower energy state to a higher energy state
B.
12.
an electron falls back from a higher energy level to a lower energy level
How is light be produced by exciting electrons with energy?
A. energy is absorbed
B. energy is released
When an electron absorbs energy of certain wavelengths, it leaps to a higher energy state
and quickly falls back to the ground state, giving off energy we sometimes see as light. The
color of light given off is determined by the amount of energy given off by the electron as it
falls to the ground state..