Unit 1 Study Guide

Which of the following ground-state electron configurations represents the atom that has the lowest first ionization energy?

• 1s²2s¹

• 1s²2s²2p²

• 1s²2s²2p⁶

• 1s²2s²2p⁶3s¹

Which of the following ground-state electron configurations represents the atom that has the lowest first ionization energy?

• 1s²2s¹

• 1s²2s²2p²

• 1s²2s²2p⁶

• 1s²2s²2p⁶3s¹

[ 1s²2s²2p⁶3s¹ ]

An electron in a 3s sublevel is farthest from the nucleus. Based on Coulomb’s law, this weakens the attractive force between the electron and nucleus, making it easier to remove.

Which of the following is the ground-state electron configuration of the F^— ion?

• 1s²2s²2p⁴

• 1s²2s²2p⁵

• 1s²2s²2p⁶

• 1s²2s²2p⁶3s²3p⁶

[ 1s²2s²2p⁶ ]

Because of its —1 charge, the fluoride ion has 10 electrons, just like an Ne atom has.

Which of the following best represents the ground-state electron configuration for an atom of selenium?

• 1s²2s²2p⁶3s²3p³

• 1s²2s²2p⁶3s²3p⁴

• 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴

• 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁵

[ 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴ ]

This configuration follows the Aufbau principle and represents 34 electrons in total.

A student is given two 10g samples, each mixture of only NaCl(s) and KCl(s) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(s)?

The mass of Cl in each mixture.

A 5.0g sample of MgCl₂ may contain measurable amounts of other compounds as impurities. Which of the following quantities is (are) needed to determine that the sample is pure MgCl₂?

The mass if Mg and the mass of Cl in the sample.

Two different ionic compounds each contain only copper and chlorine. Both compounds are powders, one white and one brown. An elemental analysis is performed on each powder. Which of the following questions is most likely to be answered by the results of the analysis?

What is the formula unit of each compound?

A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample is KCl. The student runs an experiment to determine the percent by mass of chlorine in each sample. From the results of this experiment alone, which of the following questions is most likely to be answered?

Which sample has the higher purity?

A student has samples of two pure compounds, XCLO₃ and ZCLO₃, which contain unkown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of solid residue from each sample. Which of the following questions can be answered from the results of the experiment?

Whic has the greater molar mass, X or Z?