Chemistry Reference
In-Depth Information
Answer C shows the same element but also the same isotope, because the
mass number is also the same.
12
6
6.
[B.
C
]—Carbon-12 has a mass of exactly 12 atomic mass units.
Lesson 3 - 3 Review
1.
[D. four]—Each electron is described by a set of four quantum numbers.
2.
[B. second]—The second quantum number indicates the sublevel that the
electron is found in.
3.
[D. four]—The number of sublevels that an energy level contains is equal to
the value for n. So, the third energy level (n = 3) contains 3 sublevels and
the fourth energy level (n = 4) contains 4 sublevels.
[A. s]—There are four possible values for
l
: 0, 1, 2 and 3, which correspond
to sublevels of s, p, d, and f respectively.
4.
5.
[B. 3]—I remember the number of orbitals that the sublevels contain by
remembering that the values represent the first 4 odd numbers, or 1, 3, 5,
and 7. Because “p” comes from the second word in my sentence, “some
people don't forget,” I know that I use the second odd number for the
number of orbitals it holds.
6.
[C. 8]—The total number of electrons that an energy level can hold is given
by the formula 2n
2
. Filling in 2 for n, we get 2(2
2
) = 8. So the second energy
level (n = 2) holds 8 electrons. Alternatively, we could have added up the
electrons that can be held by the sublevels. The second energy level has two
sublevels, an “s” and a “p.” The “s” sublevel can hold up to 2 electrons and
the “p” sublevel holds up to 6, for a total of 8 electrons.
Lesson 3 - 4 Review
1.
[2]—Each level has a number of sublevels that is equal to its energy level (n)
number. The first energy level (n = 1) has one sublevel, the second (n = 2)
has two, the third (n = 3) has three, and so on.
2.
[3]—The four sublevels (s, p, d, f) contain 1, 3, 5, and 7 orbitals, in that order.
The p sublevel contains 3 orbitals, which can hold up to a total of 6 electrons.
3.
[32]—The total number of electrons that an energy level can hold is given
by the formula 2 n
2
. So, when n = 4, 2(4
2
) = 32 electrons.
4.
[2]—If you got this question wrong, go back and read the question slower.
It asks how many electrons an f orbital can hold. All orbitals, regardless of
which sublevel they are in, can hold up to two electrons.
5.
[1s
2
2s
2
2p
6
3s
2
3p
6
4s
1
]—Potassium has an atomic number of 19, which
means that it has 19 protons. In a neutral atom, the number of protons is
equal to the number of electrons, so neutral potassium has 19 electrons.
