ATI TEAS SCIENCE REVIEW- CHEMISTRY
Question 1
How many protons, neutrons, and electrons does a neutral atom of Carbon-14
(¹⁴C) have?
A. 6 protons, 6 neutrons, 6 electrons
B. 6 protons, 8 neutrons, 6 electrons
C. 6 protons, 14 neutrons, 6 electrons
D. 14 protons, 6 neutrons, 14 electrons
Answer: B. 6 protons, 8 neutrons, 6 electrons
Rationale: Carbon has an atomic number of 6, meaning it always has 6 protons. In a
neutral atom, electrons equal protons (6). Carbon-14 has a mass number of 14, so
neutrons = 14 - 6 = 8.
Question 2
Which subatomic particle has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: Electrons carry a negative charge (-1). Protons carry a positive charge (+1),
and neutrons have no charge.
,Question 3
What is the maximum number of electrons that can occupy the second energy
shell (n=2)?
A. 2
B. 8
C. 18
D. 32
Answer: B. 8
Rationale: The maximum number of electrons in any shell is 2n². For n=2: 2(2²) = 2(4) =
8 electrons. The first shell holds 2, the second holds 8, the third holds 18, and the fourth
holds 32.
Question 4
Which of the following correctly identifies the electron configuration for sodium
(Na, atomic number 11)?
A. 1s²2s²2p⁶3s²
B. 1s²2s²2p⁶3s¹
C. 1s²2s²2p⁶3p¹
D. 1s²2s²2p⁶3s²3p¹
Answer: B. 1s²2s²2p⁶3s¹
Rationale: Sodium has 11 electrons. The first 10 fill the 1s, 2s, and 2p orbitals
(1s²2s²2p⁶), and the 11th electron enters the 3s orbital (3s¹). This gives the configuration
1s²2s²2p⁶3s¹.
Question 5
, Which of the following is a pair of isotopes?
A. ¹²C and ¹⁴C
B. ¹⁴N and ¹⁴C
C. ¹²C and ¹³C
D. Both A and C
Answer: D. Both A and C
Rationale: Isotopes are atoms of the same element with different numbers of neutrons.
Carbon-12 and Carbon-14 are both carbon isotopes (6 protons). Carbon-12 and
Carbon-13 are also isotopes (both carbon). ¹⁴N and ¹⁴C are different elements (different
protons).
Section 2: The Periodic Table & Periodicity
Key Concepts
Trend Direction Reason
Atomic Radius Decreases left → right Increasing nuclear charge pulls electrons closer
Atomic Radius Increases top → bottom Additional electron shells
Ionization Energy Increases left → right Stronger nuclear attraction
Ionization Energy Decreases top → bottom Electrons farther from nucleus
Electronegativity Increases left → right Stronger pull on electrons
Electronegativity Decreases top → bottom Weaker pull on electrons
Question 1
How many protons, neutrons, and electrons does a neutral atom of Carbon-14
(¹⁴C) have?
A. 6 protons, 6 neutrons, 6 electrons
B. 6 protons, 8 neutrons, 6 electrons
C. 6 protons, 14 neutrons, 6 electrons
D. 14 protons, 6 neutrons, 14 electrons
Answer: B. 6 protons, 8 neutrons, 6 electrons
Rationale: Carbon has an atomic number of 6, meaning it always has 6 protons. In a
neutral atom, electrons equal protons (6). Carbon-14 has a mass number of 14, so
neutrons = 14 - 6 = 8.
Question 2
Which subatomic particle has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: Electrons carry a negative charge (-1). Protons carry a positive charge (+1),
and neutrons have no charge.
,Question 3
What is the maximum number of electrons that can occupy the second energy
shell (n=2)?
A. 2
B. 8
C. 18
D. 32
Answer: B. 8
Rationale: The maximum number of electrons in any shell is 2n². For n=2: 2(2²) = 2(4) =
8 electrons. The first shell holds 2, the second holds 8, the third holds 18, and the fourth
holds 32.
Question 4
Which of the following correctly identifies the electron configuration for sodium
(Na, atomic number 11)?
A. 1s²2s²2p⁶3s²
B. 1s²2s²2p⁶3s¹
C. 1s²2s²2p⁶3p¹
D. 1s²2s²2p⁶3s²3p¹
Answer: B. 1s²2s²2p⁶3s¹
Rationale: Sodium has 11 electrons. The first 10 fill the 1s, 2s, and 2p orbitals
(1s²2s²2p⁶), and the 11th electron enters the 3s orbital (3s¹). This gives the configuration
1s²2s²2p⁶3s¹.
Question 5
, Which of the following is a pair of isotopes?
A. ¹²C and ¹⁴C
B. ¹⁴N and ¹⁴C
C. ¹²C and ¹³C
D. Both A and C
Answer: D. Both A and C
Rationale: Isotopes are atoms of the same element with different numbers of neutrons.
Carbon-12 and Carbon-14 are both carbon isotopes (6 protons). Carbon-12 and
Carbon-13 are also isotopes (both carbon). ¹⁴N and ¹⁴C are different elements (different
protons).
Section 2: The Periodic Table & Periodicity
Key Concepts
Trend Direction Reason
Atomic Radius Decreases left → right Increasing nuclear charge pulls electrons closer
Atomic Radius Increases top → bottom Additional electron shells
Ionization Energy Increases left → right Stronger nuclear attraction
Ionization Energy Decreases top → bottom Electrons farther from nucleus
Electronegativity Increases left → right Stronger pull on electrons
Electronegativity Decreases top → bottom Weaker pull on electrons
