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The electron configuration for an atom of calcium in the ground state is —

A. 1s²2s²2p²3s²3p³4s²
Incorrect. There are too few electrons in the 2p and 3p sublevels.

B. 1s²2s²2p¹⁰3s²3p⁴
Incorrect. There are too many electrons in the 2p sublevel.

C. 1s²2s²2p⁶3s²3p⁶4s²
Correct! All the sublevels are included with the appropriate number of electrons in them.

D. 1s²2s²3s²3p⁶3d⁸
Incorrect. 2p sublevel is not included.

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The element with the ground state electron configuration of 1s²2s²2p⁶3s²3p⁴ is —

A. Argon
Incorrect. Argon is in the 3p sublevel, but it has 6 electrons, not 4.

B. Chromium
Incorrect. Chromium is in the 3d sublevel, which is not included in this configuration.

C. Oxygen
Incorrect. Oxygen is in the 2p sublevel, whereas this configuration goes up to the 3p sublevel.

D. Sulfur
Correct! Sulfur has 4 electrons in the 3p sublevel and has 16 electrons total.

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What type(s) of sublevels are found in the third energy level?

A. s only
Incorrect. The first energy level only contains s sublevels. The third energy level has more.

B. s and p only
Incorrect. The second energy only contains s and p sublevels. The third energy level has more.

C. s, p, and d only
Correct! The third energy level does contain s, p, and d sublevels, but not an f sublevel.

D. s, p, d and f
Incorrect. The third energy level does contain s, p, and d sublevels, but not an f sublevel.

Which of the following is a valid electron configuration?

A. 1s²2s²2p⁶3s²3p⁶4s²4d¹⁰4p⁵
Incorrect. Sublevel 4d is out of sequence. Sublevel 3d comes after 4s.

B. 1s²2s²2p⁶3s²3d⁵
Incorrect. Sublevel 3d is out of sequence. Sublevel 3p comes after 3s.

C. 1s²2s²2p⁶3s³3d⁵
Incorrect. Sublevel 3s can only hold 2 electrons and in this electron configuration it notes sublevel 3s as having three electrons.

D. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s¹
Correct! This is a correct electron configuration for the element rubidium.

If an element has an f sublevel, we know that elements must have at least —

A. 1 energy level
Incorrect. The first energy level is only made up of one sublevel, sublevel s.

B. 2 energy levels
Incorrect. The second energy level is only made up of s and p sublevels.

C. 3 energy levels
Incorrect. The third energy level is made up of s, p and d sublevels.

D. 4 energy levels
Correct! The fourth energy level is made up of s, p, d and f sublevels.