Download ANSWER LOGIC

NOTE:, THE QUESTIONS AND ANSWERS ARE THE SAME
FOR EACH EXAM FORM, HOWEVER THE ANSWER CHOICES
ARE SCRAMBLED AND ARE DIFFERENT FOR EACH EXAM.
YOU MUST COMPARE THE TEST ANSWER CHOICE TO THE
ONE I PROVIDE ON THIS PPT. TO EXAMINE YOUR
SCANTRON FOR MISGRADING ERRORS. All answers on this
document are for choice one, however choice 2 answers are the
same on a different choice.
1)
Definition, atom is mainly empty space
1) Electron cloud : little mass in a large volume approximates empty space (very low
density)
2) QUESTION ANALYSIS: EASY. Find protons in a potassium-42 nuc.
ANSWER LOGIC: The proton number is the atomic number, from periodic table. For K the atomic number is 19,
which is the number of protons and your answer.
3) QUESTION ANALYSIS: Some work, EASY. Find the numbers of neutrons and protons in both atoms and
compare.
ANSWER LOGIC: Write the n and p of both atoms and compare need atomic numbers from periodic table
4
7
He
2
PROTONS = 2
Neutrons = 4-2 = 2
Li
3
PROTONS = 3
Neutrons = 7-3 = 4
All choices refer to He-4, and He has one fewer proton than Li which eliminates choices B and C
on form 1. He does not have one more neutron which eliminates choice A. He does have 2 less
neutrons which is the answer. CHOICE D.
4) QUESTION ANALYSIS: Some work, EASY. Find the numbers of electrons, neutrons and protons in both the
oxygen -18 atom and (-2) ion, then compare.
ANSWER LOGIC: Write the n and p AND ELECTRONS of both particles and compare need atomic number
from periodic table
18
18
8
O
PROTONS = 8
Neutrons = 18-8 = 10
2-6 8 ELECTRONS
8
2-(
indicative of 2 gained electrons)
O
PROTONS = 8
Neutrons = 18-8 = 10
2-8 10 ELECTRONS
The answer choices refer to the ion, which has 8 p, 10 n, 10 electrons
NOTE: ionization does not affect the nucleus.
5) For the number of valence electrons simply look up the configuration
sequence for phosphorus (P) on the periodic table. The sequence is 2-8-5,
with the last number (5 here) being the number of valence electrons,
therefore the answer is 5 valence electrons.
6) Any atom or ion emits its specific spectrum as electrons fallback to the
ground state and release energy. The first fact in each answer choice refers
to the gain or emission (loss) of energy. As electrons fall back they emit
energy,,,eliminating the choices that indicate a gain. The correct answer is
the one where the second fact indicates a return (fallback) to lower energy
levels (stability). ANS: emit energy and return to lower energy levels.
7) The word “atom” is indicative of the neutral ground state. In this state sodium
has 11 electrons with an arrangement of 2-8-1 as found on the periodic
table. Remember the periodic table gives only neutral ground state
configurations. You could have derived this from Aufbau however you would
use up more time than needed.
8) QUESTION ANALYSIS: Some work, EASY. Find the numbers of neutrons and protons in both atoms and
compare.
ANSWER LOGIC: Write the n and p of both atoms and compare need atomic numbers from periodic table
16
15
N
7
PROTONS = 7
Neutrons = 15-7 = 8
O
8
PROTONS = 8
Neutrons = 16-8 = 8
Simply subtract mass number from atomic number to get neutrons. Atomic numbers from
periodic table and the question gave you the isotopic mass number.
9) The nuclear charge is the atomic number, the nitrogen has atomic number, 7
and thus the greatest nuclear charge.
10) The mass number of an element is the weighted average of the most
abundant isotopes. The atomic mass number is usually closest to the most
abundant isotope, in this case 35X is 90% abundant and thus the mass
number will be closest to 35 amu.
11) Facts: metals are toward the left of a period and nonmetals are toward the
right. We also know that electronegativity and ionization energy INCREASE
to the nonmetal right as radius decreases. Therefore the metals on the left
have larger radii.
NOTE: the answer choices refer to the metals.
12) QUESTION ANALYSIS: Some work, EASY.
ANSWER LOGIC: First write the configuration of the chlorine atom (neutral ground state), then add one electron
from the ground for each – charge. Cl needs one more electron to complete a third shell octet therefore it will gain
one to become a -1 ion. Because the negative ion has more electrons and a larger electron cloud…it will be larger.
35
35
17
Cl
PROTONS=ELECTRONS = 17
17
-1
Cl
PROTONS = 17, ELECTRONS =18
13)FACTS, radius increases down a group and to the left of a period, find the
sequence that follows that trend. Radius decreases up and to the right,
another trend to look for. In this question look for increasing radii by finding a
sequence of elements down a group or right to left across a period. The
radius of F<Cl<Br<I is a sequence of increasing atomic radii as you read
down the group #17( the halides). You could also look the radii up on table S,
but this kills time bubbies.
14) Nonmetals have high ionization energy, which eliminates the choices with
low ionization energy for the first fact also nonmetals are poor conductors as
they hold the electrons tightly (no mobile electrons in non metals). The
answer is high ionization energy and poor electrical conductivity. NOTE the
answer choices refer to nonmetals.
15) The lowest ionization energy will be at the bottom of a group or to the left,
usually a metal. Sr is the most bottom left of the choices and would have the
lowest ionization energy. Looking o table S will give the same answer but
will be time consuming.
16) Group 18 (noble gasses) all have stable valence shells. He has a full first
and all of the others have valence octets.
17) Look for an excited state with 9 electrons (the atomic mass of Cl is 9, so 9
protons therefore 9 electrons). Also look for a configuration with 9 electrons
that violates the Aufbau process.
This electron was promoted
18) QUESTION ANALYSIS: Some work, EASY.
ANSWER LOGIC: Calculate the electron number by adding one electron to the ground state for each
negative charge and removing from the ground state one electron for each positive charge.
9
4
9
Be
4
ATOM:PROTONS=ELECTRONS = 4
Be
+2 (2 lost electrons)
ION:PROTONS= 4,ELECTRONS =2
2-2 atom has 2 more electrons
2
19) During excitation the electron absorbs energy as it rises to a higher energy
level, which excites and destabilizes it. No emission of light occurs during
excitation.
20) All elements in a group have identical valence configuration and valence
electron number. For group 13 it is three electrons as the atoms all end in a
three in the configuration sequence.
21)As a group is read down, the radii increase (eliminates the choices that say
decrease) and the ionization energies decrease. See notes
22) All negative ions are larger than the neutral atom because they have more
electrons and a larger cloud. Remember each – charge represents a gained
electron. S-2 is larger and has 2. more electrons.
23) The atom with the lowest ionization energy loses electrons most easily. You
can look up ionization energies on table S (time intensive), or better use the
trends. Ionization energy decreases down and to the left as is Rb relative to
the other choices. Rb is the answer. Remember as ionization energy
decreases the probability of removing an electron decreases.
24)Elements that tend to gain electrons have high electronegativity and high
ionization energy…both from strong effective nuclear charge.
25) By definition non metals have higher electronegativities and higher
ionization energies. Note the answer choices refer to non metals.
26) The tendency of an atom to attract (and hold ) electrons is given by
electronegativity. Look for the element closest to the right top of the periodic
table. You could use table s also if you have the time. Nitrogen “N” is the
answer.
27) As you read down any group, the number of shells (principle quantum
number) increases.
28) An orbital is the most likely region of electron cloud probability.
29) The lowest energy level is n=1, close to the nucleus.