Topics include: Atomic models, symbols and atomic numbers of elements, neutrons, isotopes, electron configurations, Lewis dot structures and ions.
June 2023
1.
SOLUTION
Nucleus of an atom contains protons (positively charged) and neutrons (no charge). Nucleus has an overall positive charge.
Answer: 1
2.
SOLUTION
A neutron and a proton have a mass of approximately one atomic mass unit. Electron is very very small compared to protons and neutrons.
Answer: 3
3.
SOLUTION
The wave-mechanical model of the atom describes the location of electrons as orbitals outside the nucleus.
Answer: 4
4.
SOLUTION
Solution:The dots represent the number of valence electrons (electrons in the outer shell). Looking at the Periodic Table, we can see the electron configuration of nitrogen is 2-5. The last number is 5 which means nitrogen has 5 valence electrons. We are looking for a structure with 5 dots.
Answer:2
5.
SOLUTION
Mass number = number of neutrons + number of protons. Number of protons is equal to the atomic number. We can find the atomic number of potassium on the Periodic Table. It is 19. Therefore, we have 37 = 19+x, x= 18
Answer: 2
January 2024
6.
SOLUTION
Electrons surround the nucleus of any atom. Protons and neutrons are located inside the nucleus.
Answer: 1
7.
SOLUTION
Gold foil experiment resulted in the following conclusions: most of the atom is empty space, inside an atom there is a small, dense, positively charged nucleus.
Answer: 2
8.
SOLUTION
The mass of each proton and neutron is 1 atomic mass unit (u).
Answer: 3
9.
SOLUTION
The further away an electron is from the nucleus, the greater its energy is. An electron in the third shell should have more energy than an electron in the second shell.
Answer: 4
10.
SOLUTION
As an atom goes from the ground state to the excited state, it absorbs energy.
Answer: 1
11.
SOLUTION
We can check Periodic table to find an electron configuration of each atom. The electron configuration of neon is 2-8. Now, let’s look at the answer choices. K electron configuration is 2-8-8-1. K+ means there is one less electron. K+ electron configuration is 2-8-8. Li electron configuration is 2-1. Li+ electron configuration will be 2. F electron configuration is 2-7. F– has one extra electron and should have an electron configuration of 2-8.
Answer:3
January 2023
12.
SOLUTION
Gold foil experiment led to the following conclusions: most of the atom is empty space, inside an atom there is a small, dense, positively charged nucleus.
Answer: 1
13.
SOLUTION
Protons and neutrons have a mass approximately equal to one atomic mass unit.
Answer: 4
14.
SOLUTION
When an electron moves from a lower to a higher energy state, it absorbs energy. When an electron moves from a higher to a lower energy state, it emits energy. Since this electron emits energy we are looking for going from a higher to a lower state.
Answer: 4
15.
SOLUTION
Protons have a charge of +1, neutrons have no charge and electrons have a charge of -1. 15 protons and 18 electrons are 15 positive charges and 18 minus charges. +15-18 = -3
Answer: 4
August 2023
16.
SOLUTION
An orbital is defined as a region of the most probable electron location according to the wave-mechanical model of an atom. The facts that there are 10 electrons and that the atom is neon are irrelevant.
Answer: 2
17.
SOLUTION
Isotopes are atoms of the same element (same atomic number=same number of protons) that have a different mass number (different number of neutrons).
Answer: 3
18.
SOLUTION
Atomic number of an element is equal to the number of protons. Atomic number can be found on the Periodic Table, on the left bottom corner of each element. Silicon has an atomic number of 14.
Answer: 2
19.
SOLUTION
Nucleus of any atom contains protons and neutrons. Protons are positively charged and neutrons are neutral. Therefore, nucleus should be positive, eliminating choices 1 and 2. Fluorine can be found on the Periodic Table and has an atomic number of 9 (bottom left number). Therefore, it has 9 protons and a charge of +9
Answer: 3
20.
SOLUTION
Cathode ray tube experiments led to the discovery of electrons.
Answer: 1
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