June 2023
1 Which phrase describes the nucleus of any atom? (1) has an overall positive charge
(2) has an overall negative charge
(3) contains negative electrons
(4) contains positive electrons
Solution: Nucleus of an atom contains protons (positively charged) and neutrons (no charge). Nucleus has an overall positive charge.
Answer: 1
2 Which two particles each have a mass of approximately one atomic mass unit? (1) an electron and a proton
(2) an electron and a positron
(3) a neutron and a proton
(4) a neutron and a positron
Solution: A neutrons 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 The wave-mechanical model of the atom describes the location of electrons (1) as loosely packed in the nucleus of an atom
(2) as densely packed in the nucleus of an atom
(3) in circular paths around the nucleus (4) in orbitals outside the nucleus
Solution: The wave-mechanical model of the atom describes the location of electrons as orbitals outside the nucleus.
Answer: 4
31 Which Lewis electron-dot diagram represents an atom of nitrogen in the ground state?
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. Alternately, Group 1 has 1 valence electron, 2 is 2 valence electrons, group 13 is 3, 14 is 4, 15 is 5, 16 is 6, 17 is 7 and 18 is 8.
Answer:2
33 A potassium atom has a mass number of 37. What is the number of neutrons in this atom? (1) 15
(2) 18
(3) 22
(4) 37
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 2023
1 Which conclusion was developed as a result of the gold foil experiment? (1) Atoms are mostly empty space. (2) All atoms are hard, indivisible spheres.
(3) Atoms have different volumes. (4) All atoms have the same volume.
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
2 Which two particles each have a mass approximately equal to one atomic mass unit? (1) positron and proton
(2) positron and electron
(3) neutron and electron
(4) neutron and proton
Solution: Protons and neutrons have a mass approximately equal to one atomic mass unit. Electron is very light and positron has the same weight as an electron but opposite charge.
Answer: 4
3. An excited potassium atom emits a specific amount of energy when one of its electrons moves from
(1) the first shell to the fourth shell
(2) the second shell to the fourth shell
(3) the fourth shell to the fifth shell
(4) the fourth shell to the second shell
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 higher to lower state.
Answer: choice 4
What is the net charge of a monatomic ion that has 15 protons, 16 neutrons, and 18 electrons?
(1) 2+
(2) 2-
(3) 3+
(4) 3-
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: Choice 4
August 2022
1. What is the number of protons in an atom with the electron configuration of 2-5?
(1) 5
(2) 2
(3) 3
(4) 7
Solution: Refer to the Periodic Table on the Reference Tables for Physical Setting/CHEMISTRY.
Every element has at the bottom. Nitrogen has a 2-5 electron configuration on the Periodic Table. The number of protons in an atom is equal to the atomic number which is the bottom left corner. The atomic number is equal to 7. Alternatively, the number of electrons is equal to the number of protons in a neutral atom. So we can just add 2+5 = 7
Answer: 4 is the correct answer.
2 In the wave-mechanical model of an atom, an orbital is defined as
(1) a region of the most probable neutron location
(2) a region of the most probable electron location
(3) the straight-line path of a neutron
(4) the straight-line path of an electron
Solution: An orbital is defined as a region of the most probable electron location according to the wave-mechanical model of an atom. This is something you need to memorize in order to answer the question correctly.
Answer: 2
5 All atoms of an element have the same (1) mass number (2) atomic mass (3) number of neutrons
(4) number of protons
Solution: All atoms of an element MUST have the same number of protons (which is equal to the atomic number). Atomic number to an element is like a social security number to a person. Each element has a unique atomic number that is specific to it.
Answer: 4
13 All atoms of the element vanadium must have the same (1) atomic number (2) mass number (3) number of neutrons plus electrons
(4) number of protons plus neutrons
Solution: All atoms of the same element (in this case vanadium) must have the same number of protons, which is also equal to the atomic number.
Answer: 1
32 What is the approximate mass of an atom that has 10 electrons, 10 protons, and 9 neutrons?
(1) 10u
(2) 19u
(3) 20u
(4) 29u
Solution:The mass of a an atom is equal to the sum of protons and neutrons. 10+9=19
Answer: 2
33 Which electron configuration represents the electrons of an atom in an excited state?
(1) 2-7-3
(2) 2-8-2
(3) 2-8-8-1
(4) 2-8-9-2
Solution: An electron in an excited state is an electron that moved from the ground state to a higher energy level. The first level has a maximum of 2 electrons, the second level has a maximum of 8 electrons. As we see in the answer choice 1, instead of being 2-8-2, the electron moved from the second energy level to the third becoming 2-7-3.
Answer: 1
June 2022
1 Which subatomic particles are matched with their charges?
(1) Protons are positive and neutrons are negative.
(2) Protons are positive and electrons are negative.
(3) Protons are negative and neutrons have no charge.
(4) Protons are negative and electrons have no charge.
Solution: Protons are positively charged, electrons are negatively charged, and neutrons are neutral.
Answer: 2
2 Which conclusion directly resulted from the “gold foil experiment”?
(1) Atoms are mostly empty space.
(2) Atoms are hard, indivisible spheres.
(3) Electrons are located in shells.
(4) Electrons have a small mass.
Solution: The gold foil experiment led to the conclusion that most of the atom is empty space and there is a small dense nucleus inside.
Answer: 1
9 Krypton atoms in the ground state tend not to bond with other atoms because their
(1) second electron shell contains eight electrons
(2) third electron shell contains eighteen electrons
(3) innermost electron shell contains two electrons
(4) outermost electron shell contains eight electrons
Explanation: Noble gases are elements in group 18 on the Periodic Table. Noble gases are very stable because they have a filled outer shell of electrons (8).
Answer: 4
31 Which electron configuration represents the electrons of a phosphorus atom in an excited state?
(1) 2-8-5
(2) 2-8-6
(3) 2-7-6
(4) 2-7-4
Explanation: Let's take a look at the Periodic Table and find phosphorus (P). On the Periodic Table, the electron configuration for P is 2-8-5. This is a ground electron configuration. For excited energy level, one electron will move to the higher energy level, such as 2-7-6. Electron moved from second energy level to the third.
Answer: 3
January 2020
1 Which statement describes a concept included in the wave-mechanical model of the atom?
(1) Protons, neutrons, and electrons are located in the nucleus.
(2) Electrons orbit the nucleus in shells at fixed distances.
(3) Atoms are hard, indivisible spheres.
(4) Electrons are located in regions called orbitals.
Solution: According to the wave-mechanical model of the atom electrons are located in regions called orbitals.
Answer: 4
2 As an electron in an atom moves from a higher energy state to a lower energy state, the atom (1) becomes a negative ion
(2) becomes a positive ion
(3) releases energy (4) absorbs energy
Solution: When an electron in an atom moved from higher energy (excited state) to lower energy state, the atom releases energy.
Answer: 3
3 Two atoms that are different isotopes of the same element have
(1) the same number of protons and the same number of neutrons
(2) the same number of protons but a different number of neutrons
(3) a different number of protons but the same number of neutrons
(4) a different number of protons and a different number of neutrons
Solution: Isotopes are atoms of the same element (same atomic number which means same number of protons) that have different mass (different number of neutrons).
Answer:2
9 Which part of a calcium atom in the ground state is represented by the dots in its Lewis electron- dot diagram? (1) the electrons in the first shell
(2) the electrons in the fourth shell
(3) the protons in the nucleus (4) the neutrons in the nucleus
Solution: Dots in the Lewis electron- dot diagram represent valence electrons (electrons in the outermost shell). Looking at the Periodic Table, we see that the electron configuration for calcium is 2-8-8-2. This means it has 2 electrons in the first shell, 8 in the second shell, 8 in the third shell and 2 in the fourth shell. It must have 2 valence electrons in the fourth shell.
Answer: 2
32 Which electron configuration could represent the electrons in a sodium atom in an excited state?
(1) 2-8
(2) 2-8-1 (3) 2-7-1
(4) 2-7-2
Solution: The electron configuration for sodium in its most stable, ground state can be found on the Periodic Table. It is 2-8-1. When an electron gets excited, it goes to the higher energy level. For example, 2-7-2, means that the electron from the second level jumped to the third level.
Answer: 4
33 What is the number of valence electrons in a nitrogen atom in the ground state? (1) 5
(2) 2
(3) 7
(4) 14
Solution:Looking at the Periodic Table, Group 1 has 1 valence electron, 2 is 2 valence electrons, Group 13 is 3, 14 is 4, 15 is 5, 16 is 6, 17 is 7 and 18 is 8. Nitrogen is in Group 15 on the Periodic Table. We can also check its electron configuration as written on the Periodic Table which is 2-5. The last number is the number of valence electrons.
Answer: 1
August 2019
1 Which statement describes the earliest model of the atom?
(1) An atom is an indivisible hard sphere.
(2) An atom has a small, dense nucleus.
(3) Electrons are negative particles in an atom.
(4) Electrons in an atom have wave-like properties.
Solution: The earliest model of an atom proposed that an atom is an indivisible hard sphere.
Answer:1
2 In all atoms of bismuth, the number of electrons must equal the
(1) number of protons
(2) number of neutrons
(3) sum of the number of neutrons and protons
(4) difference between the number of neutrons and protons
Solution: In a neutral atom of any element, the number of electrons must be equal to the number of protons.
Answer:1
4 An orbital is a region in an atom where there is a high probability of finding
(1) an alpha particle
(2) an electron (3) a neutron
(4) a positron
Solution: An orbital is defined as a region in an atom where there is a high probability of finding an electron.
Answer: 2
5 Which electron shell in an atom of calcium in the ground state has an electron with the greatest amount of energy? (1) 1
(2) 2 (3) 3
(4) 4
Solution: The further electrons are located from the nucleus, the greater is their amount of energy. We can locate calcium on the Periodic Table and see that its' electron configuration is 2-8-8-2. This means it has 2 electrons in the first shell, 8 in the second shell, 8 in the third shell and 2 in the fourth shell. The last electrons shell must have an electron with the greatest amount of energy. In this case, this is shell number 4.
Answer: 4
32 Which electron configuration represents the electrons in an atom of sulfur in an excited state? (1) 2 – 8 – 6
(2) 2 – 7 – 7
(3) 2–8– 7
(4) 2–7– 8
Solution: The electron configuration for sulfur in its most stable, ground state can be found on the Periodic Table. It is 2-8-6. When an electron gets excited, it goes to the higher energy level. For example, 2-7-7, means that the electron from the second level jumped to the third level.
Answer: 2
33 Which notations represent atoms that have the same number of protons but a different number of neutrons?
(1) H-3 and He-3
(2) S-32 and S-32 (3) Cl-35 and Cl-37
(4) Ga-70 and Ge-73
Solution: Atoms with the same number of protons must be atoms of the same element. We can eliminate choices 1 and 4. Different number of neutrons means different atomic mass which is written after the elements in the answer choices. We can eliminate choice 2.
Answer: 3
Ps: atoms of the same element with different number of neutrons are called isotopes.
June 2019
1. Which particles are found in the nucleus of an argon atom?
(1) protons and electrons
(2) positrons and neutrons
(3) protons and neutrons
(4) positrons and electrons
Solution: Nucleus of any atom contains protons and neutrons.
Answer: 3
2 The diagram below represents a particle traveling through an electric field.
Which particle remains undeflected when passing through this electric field?
(1) proton (2) electron (3) neutron (4) positron Solution: We see positive charges on the top plane and negative charges on the bottom plane. In order to remain undeflected, the particle must have no charge. Answer: Neutron is the only particle that has no charge out of the answer choices listed. Choice 3 is correct. 3 The mass of an electron is
(1) equal to the mass of a proton
(2) equal to the mass of a neutron (3) greater than the mass of a proton (4) less than the mass of a neutron Solution: Electron has a very small mass (1/2000) when compared to that of proton or neutron. Answer: Choice 4 should be the correct answer choice. 4 Compared to the energy of an electron in the second shell of an atom of sulfur, the energy of an electron in the
(1) first shell is lower
(2) first shell is the same (3) third shell is lower (4) third shell is the same Solution: The higher the shell number of an electron, the further it is from the nucleus and the more energy it has. Answer: 1 is correct 5 In the ground state, an atom of which element has seven valence electrons?
(1) sodium (2) phosphorus (3) nitrogen (4) fluorine Solution: Number of valence electrons is equal to the group number on the Periodic Table (For groups 13-18 only count the second number). All elements in group 17 must have seven valence electrons. Fluorine is in group 17. Answer: choice 4
32 Which electron configuration represents an atom of chlorine in an excited state?
(1) 2-8-7-2
(2) 2-8-7
(3) 2-8-8
(4) 2-7-8
Solution: In an excited state, one electron jumps from a lower to a higher energy level. Looking at the Periodic Table, the electron configuration for chlorine is 2-8-7 in the ground state. In the excited state, we need to see an electron go to the higher energy such as 2-7-8, an electron went from second to third energy level.
Answer: Choice 4
January 2019
1 The results of the gold foil experiment led to the conclusion that an atom is
(1) mostly empty space and has a small, negatively charged nucleus
(2) mostly empty space and has a small, positively charged nucleus
(3) a hard sphere and has a large, negatively charged nucleus
(4) a hard sphere and has a large, positively charged nucleus
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: 2
2 Atoms are neutral because the number of
(1) protons equals the number of neutrons
(2) protons equals the number of electrons
(3) neutrons is greater than the number of protons
(4) neutrons is greater than the number of electrons
Solution: Protons have a +1 charge and electrons have a -1 charge. Neutrons are neutral. Atoms are neutral because their number of protons equals the number of electrons.
Answer: 2
3 In the ground state, valence electrons of a krypton atom are found in
(1) the first shell (2) the outermost shell (3) both the nucleus and the first shell (4) both the first shell and the outermost shell
Solution: Valence electrons of an atom of any element are electrons that are found in the outermost shell.
Answer: 2
4 According to the wave-mechanical model of the atom, electrons are located in (1) orbitals (2) circular paths (3) a small, dense nucleus
(4) a hard, indivisible sphere
Solution: According to the wave-mechanical model of the atom, electrons are located in orbitals
Answer: 1
5 Which electron configuration represents the electrons in an atom of sodium in the ground state at STP?
(1) 2-8-1
(2) 2-7-2 (3) 2-8-6
(4) 2-7-7
Solution: We can find the electron configuration of an atom of sodium (Na) in the ground state on the Periodic Table. It is located at the bottom of the sodium block and is 2-8-1
Answer: 1
31 The three nuclides, U-233, U-235, and U-238, are isotopes of uranium because they have the same number of protons per atom and (1) the same number of electrons per atom
(2) the same number of neutrons per atom
(3) a different number of electrons per atom
(4) a different number of neutrons per atom
Solution: Isotopes of an elements have the same number of protons but a different number of neutrons.
Answer: 4
August 2018
1 According to the wave-mechanical model, an orbital is defined as the most probable location of
(1) a proton
(2) a neutron (3) a positron
(4) an electron
Solution: According to the wave-mechanical model, an orbital is defined as the most probable location of an electron
Answer: 4
2 The part of an atom that has an overall positive charge is called (1) an electron
(2) the nucleus (3) the first shell (4) the valence shell
Solution: The nucleus of an atom contains protons (positively charged) and neutrons (neutral), making its overall charge positive. Electrons are negatively charged.
Answer: 2
3 Which subatomic particles each have a mass of approximately 1 u? (1) proton and electron
(2) proton and neutron
(3) neutron and electron
(4) neutron and positron
Solution: Protons and neutrons each have a mass of approximately 1 u
Answer: 2
4 The discovery of the electron as a subatomic particle was a result of (1) collision theory (2) kinetic molecular theory (3) the gold-foil experiment (4) experiments with cathode ray tubes
Solution: The discovery of the electron as a subatomic particle was a result of experiments with cathode ray tubes.
Answer: 4
32 Which electron configuration represents the electrons of an atom in an excited state? (1) 2-5
(2) 2-8-5
(3) 2-5-1
(4) 2-6
Solution: In an atom the first shell can hold a maximum of 2 electrons, the second shell holds a maximum of 8 and the third holds a maximum of 8. Electrons in an excited state have moved from lower energy level to the higher energy level. We can see that in 2-5-1 electron configuration, an electron moved from the second energy level to the third. Otherwise, we would see 2-6 since the second energy level has a maximum of 8 electrons.
Answer: 3
January 2018
1 Which statement describes the location of 5 protons and neutrons in an atom of helium?
(1) Protons and neutrons are in the nucleus.
(2) Protons and neutrons are outside the nucleus.
(3) Protons are outside the nucleus, and neutrons are in the nucleus.
(4) Protons are in the nucleus, and neutrons are outside the nucleus.
Solution: Protons and neutrons are always located inside the nucleus. Electrons are located outside the nucleus.
Answer: 1
2 Given a list of atomic model descriptions: A: electron shells outside a central nucleus
B: hard, indivisible sphere C: mostly empty space Which list of atomic model descriptions represents the order of historical development from the earliest to most recent?
(1) A,B,C
(2) A,C,B (3) B,C,A
(4) B,A,C
Solution: The earliest model of an atom proposed that it is a hard, indivisible sphere. Later, the golf foil experiment proved that an atom consists of mostly empty space. Finally, it was discovered that electrons are outside the nucleus.
Answer: 3
31 An ion that consists of 7 protons, 9 neutrons, and 10 electrons has a net charge of
(1) 2-
(2) 2+ (3) 3+
(4) 3-
Solution: An electron has a charge of -1. A proton has a charge of +1. A neutron has a charge go 0. 7 protons is +7 and 10 electrons is -10. +7-10= -3
Answer: 4
32 Which electron configuration represents the electrons of an atom in an excited state?
(1) 2–2
(2) 2–2–1 (3) 2–8
(4) 2–8–1
Solution: When an electron is excited, it moves from a lower energy level to higher. The first energy level has a maximum of 2 electrons. The second energy level has a maximum of 8 electrons. The third energy level has a maximum of 8 electrons. If we look at choice 2, we see 2-2-1. This means 2 electrons in the first enegy level, 2 electrons in the second energy level and 1 in the third energy level. We know that the second level has a maximum of 8 electrons. Yet, it has only 2 electrons and another electron in the third level. This means that one of the electrons in the second level went up to the third level (got excited).
Answer: 2
June 2018
1 Which statement describes the charge and location of an electron in an atom?
(1) An electron has a positive charge and is located outside the nucleus.
(2) An electron has a positive charge and is located in the nucleus.
(3) An electron has a negative charge and is located outside the nucleus.
(4) An electron has a negative charge and is located in the nucleus.
Solution: An electron has a negative charge and is located outside the nucleus.
Answer: 3
2 Which statement explains why a xenon atom is electrically neutral?
(1) The atom has fewer neutrons than electrons.
(2) The atom has more protons than electrons.
(3) The atom has the same number of neutrons and electrons.
(4) The atom has the same number of protons and electrons.
Solution: An electron has a charge of -1. A proton has a charge of +1. A neutron has a charge go 0. An atom is electrical neutral when there are equal number of protons and electrons.
Answer: 4
3 If two atoms are isotopes of the same element, the atoms must have
(1) the same number of protons and the same number of neutrons
(2) the same number of protons and a different number of neutrons
(3) a different number of protons and the same number of neutrons
(4) a different number of protons and a different number of neutrons
Solution: Isotopes are atoms of the same element (same number of protons) with a different number of neutrons.
Answer: 2
4 Which electrons in a calcium atom in the ground state have the greatest effect on the chemical properties of calcium? (1) the two electrons in the first shell (2) the two electrons in the fourth shell
(3) the eight electrons in the second shell
(4) the eight electrons in the third shell
Solution: Valence electrons (electrons in the outermost shell) have he greatest effect on the chemical properties of an element. Looking on the Periodic Table, we see the electron configuration for calcium is 2-8-8-2 (2 electrons in the first shell, 8 in the second shell, 8 in the third shell and 2 in the fourth shell). The fourth shell is the outermost shell and has two electrons.
Answer: 2
5 The weighted average of the atomic masses of the naturally occuring isotopes of an element is the (1) atomic mass of the element
(2) atomic number of the element
(3) mass number of each isotope
(4) formula mass of each isotope
Solution: Atomic mass of an element is the weighted average of the atomic masses of the naturally occurring isotopes of an element.
Answer: 1
33 The table below shows the number of protons, neutrons, and electrons in four ions.
Which ion has a charge of 2-?
(1) A (2) E
(3) G
(4) J
Solution: An electron has a charge of -1. A proton has a charge of +1. A neutron has a charge go 0. To have a 2- charge an ion must have two more electrons than protons.
Answer: 1
34 What is the approximate mass of an atom that contains 26 protons, 26 electrons and 19 neutrons?
(1) 26 u
(2) 45 u (3) 52 u
(4) 71 u
Solution: Mass is equal to the sum of protons and neutrons. 26 protons + 19 neutrons = 45 atomic mass units.
Answer: 2
35 Which electron configuration represents a potassium atom in an excited state? (1) 2-7-6
(2) 2-8-5
(3) 2-8-8-1
(4) 2-8-7-2
Solution: When an electron is excited, it moves from a lower energy level to higher. We can find potassium's(K) electron configuration on the Periodic Table. It is 2-8-8-1.This means 2 electrons in the first energy level, 8 in the second, 8 in the third and 1 in the fourth. If we look at choice 4, we see 2-8-7-2. One of the electrons in the third energy level moved up to the fourth energy level.
Answer: 4
36 What is the total number of neutrons in an atom of K-42? (1) 19
(2) 20
(3) 23
(4) 42
Solution: Mass number = number of protons + number of neutrons. The mass number of K is given to us in the question and is 42. Next, the number of protons is equal to the atomic number and can be found on the Periodic Table. The atomic number of K is 19. Now we can find the number of neutrons.
42 = 19+x
X= 23
Answer: 3
June 2017
1 Which statement describes the structure of an atom?
(1) The nucleus contains positively charged electrons.
(2) The nucleus contains negatively charged protons.
(3) The nucleus has a positive charge and is surrounded by negatively charged electrons.
(4) The nucleus has a negative charge and is surrounded by positively charged electrons.
Solution: The nucleus contains protons (positively charged) and neutrons (neutral). Negatively charged electrons are located outside of the nucleus.
Answer: 3
2 Which term is defined as the region in an atom where an electron is most likely to be located?
(1) nucleus
(2) orbital (3) quanta
(4) spectra
Solution: Orbital is defined as the region in an atom where an electron is most likely to be located
Answer: 2
3 What is the number of electrons in an atom of scandium? (1) 21
(2) 24 (3) 45
(4) 66
Solution: In a neutral atom, the number of protons is equal to the number of electrons. All we need to do is to find the number of protons for scandium. Atomic number equals the number of protons. We can find atomic number on the Periodic Table at the bottom of the element. It is 21 for scandium. This means there are 21 protons and 21 electrons in an atom of scandium.
Ps: Not sure what the symbol for scandium is? Table S on the Reference Table has the names of the elements as well as abbreviations.
Answer: 1
4 Which particle has the least mass? (1) a proton (2) an electron
(3) a helium atom
(4) a hydrogen atom
Solution: An electron is very small and has a very small amount of mass compared to the mass of a proton. Helium atom has 2 protons (atomic number) and a hydrogen atom has 1 proton.
Answer: 2
5 Which electron transition in an excited atom results in a release of energy? (1) first shell to the third shell (2) second shell to the fourth shell
(3) third shell to the fourth shell
(4) fourth shell to the second shell
Solution: When an electron moves from a higher to a lower energy level (shell), it releases energy.
Answer:4
6 On the PeriodicTable ,the number of protons in an atom of an element is indicated by its (1) atomic mass (2) atomic number (3) selected oxidation states (4) number of valence electrons
Solution: Atomic number is equal to the number of protons in an atom of an element.
Answer: 2
31 Which electron configuration represents the electrons of an atom of neon in an excited state? (1) 2-7
(2) 2-8
(3) 2-7-1
(4) 2-8-1
Solution: When an electron goes from a lower to a higher energy level, it is in an excited state. The first energy level has a maximum of 2 electrons. Second energy level has a maximum of 8 electrons. Third energy level has a maximum of 8 electrons. If we take a look at choice 3, 2-7-1. It means two electron in the first energy level, seven in the second energy level and one in the third energy level. Since second energy level has a maximum of 8 electrons, we can see that one electron from the second energy level jumped to the third energy level.
Answer: 3
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