Q: Given the following isotopes of chlorine: $$^{35}\mathrm{Cl} ($$mass = 34.97 amu, abundance = 75.77%) and $$^{37}\mathrm{Cl} ($$mass = 36.97 amu, abundance = 24.23%), calculate the average atomic mass of chlorine.

$$(34.97 \times 0.7577) + (36.97 \times 0.2423) = 35.45$$ amu

Question 1

Which of the following statements correctly describes the charge, mass, and location of a neutron in an atom?

Accepted Answer

Neutrons have no charge, mass of approximately 1 amu, and are located in the nucleus.

Question 2

A neutral atom of magnesium has an atomic number of 12 and a mass number of 25. How many protons, neutrons, and electrons does it contain?

Accepted Answer

12 protons, 13 neutrons, 12 electrons

Question 3

Given the following isotopes of chlorine: $$^{35}\mathrm{Cl} ($$mass = 34.97 amu, abundance = 75.77%) and $$^{37}\mathrm{Cl} ($$mass = 36.97 amu, abundance = 24.23%), calculate the average atomic mass of chlorine.

Accepted Answer

$$(34.97 	imes 0.7577) + (36.97 	imes 0.2423) = 35.45$$ amu

Question 4

Which of the following elements is a metalloid (semimetal)?

Accepted Answer

Silicon (Si)

Question 5

Which element in the following set has the largest atomic radius: Na, Mg, Al, Si?

Accepted Answer

Na

Question 6

Which group on the periodic table is known as the alkali metals?

Accepted Answer

Group 1

Question 7

What is the abbreviated electron configuration for calcium ($$\mathrm{Ca}$$, atomic number 20)?

Accepted Answer

$$[\mathrm{Ar}]\ 4s^2$

Question 8

How many valence electrons does a neutral atom of phosphorus ($$\mathrm{P}$$, atomic number 15) have?

Accepted Answer

5

Question 9

Which of the following ions is isoelectronic with neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{F}^-$$

Question 10

Which of the following compounds is ionic?

Accepted Answer

$$\mathrm{NaCl}$$

Question 11

What is the correct formula for ammonium sulfate?

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 12

Which of the following molecules has a trigonal planar geometry?

Accepted Answer

$$\mathrm{BF}_3$$

Question 13

Which of the following molecules is polar?

Accepted Answer

$$\mathrm{H_2O}$$

Question 14

Which of the following intermolecular forces is the strongest?

Accepted Answer

Hydrogen bonding

Question 15

Which of the following best explains why fluorine has a higher first ionization energy than lithium?

Accepted Answer

Fluorine has a greater nuclear charge and a smaller atomic radius than lithium.

Question 16

Which of the following is the correct electron-dot (Lewis) structure for methane ($$\mathrm{CH}_4$$)?

Accepted Answer

A central C atom with four single bonds to four H atoms, each H with no lone pairs.

Question 17

Which of the following best describes the trend in atomic radius across a period from left to right?

Accepted Answer

Atomic radius decreases due to increasing nuclear charge.

Question 18

Which of the following is the correct name for $$\mathrm{FeCl}_3$$?

Accepted Answer

Iron(III) chloride

Question 19

Which of the following pairs of ions would form an ionic compound with the formula $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

$$\mathrm{Ca}^{2+}$$ and $$\mathrm{NO_3$}^-$$

Question 20

Which of the following best describes the electron configuration of the oxide ion ($$\mathrm{O}^{2-}$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

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