Question

section 5.1 what are elements?, continued
in your textbook, read about electrons in energy levels and isotopes.
circle the letter of the choice that best completes the statement or answers the question.

1. how many electrons can be held in the innermost energy level of atoms?

a. 2 b. 8 c. 18 d. 32

1. how many electrons can the fourth energy level hold?

a. 2 b. 8 c. 18 d. 32

1. many elements are mixtures of

a. oxygen. b. electrons. c. neutrons. d. isotopes.

1. the chemical behavior of different elements is determined by the

a. number of electrons in the innermost energy level.
b. number of electrons in the middle energy level.
c. number of electrons in the outermost energy level.
d. total number of electrons in all of the energy levels.

1. how many electrons can an atoms third energy level hold?

a. 2 b. 8 c. 18 d. 32

1. elements with a full outermost energy level are

a. unlikely to combine chemically with other elements.
b. likely to combine chemically with other elements.
c. likely to combine with inert elements.
d. likely to combine with many elements at one time.

1. the identity of an element is defined by its number of

a. electrons.
b. protons.
c. neutrons.
d. isotopes.

1. how many electrons can an atoms second energy level hold?

a. 2 b. 8 c. 18 d. 32

Explanation:

• Question 14: The innermost energy level (K - shell) can hold a maximum of 2 electrons.
• Question 15: The formula for the number of electrons in an energy level is \(2n^{2}\), where \(n\) is the energy level number. For \(n = 4\), \(2\times4^{2}=2\times16 = 32\).
• Question 16: Many elements are mixtures of isotopes. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
• Question 17: The chemical behavior of different elements is determined by the number of electrons in the outermost energy level (valence electrons).
• Question 18: For \(n = 3\), using the formula \(2n^{2}\), \(2\times3^{2}=2\times9 = 18\).
• Question 19: Elements with a full outermost energy level (noble gases) are unlikely to combine chemically with other elements as they have a stable electron configuration.
• Question 20: The identity of an element is defined by its number of protons.
• Question 21: For \(n = 2\), using the formula \(2n^{2}\), \(2\times2^{2}=2\times4 = 8\).

Answer:

1. a. 2
2. d. 32
3. d. isotopes
4. c. number of electrons in the outermost energy level
5. c. 18
6. a. unlikely to combine chemically with other elements
7. protons (assuming option b is protons, as it's cut - off in the original)
8. b. 8