General orrganic and biological chemistry structures off liffe 5th by karen timberlake04 worked examples

© 2016 Pearson Education, Inc.General, Organic, and Biological Chemistry: Structures of Life, 5/e Complete the following table with the correct symbol or name of each element: Sample Pro

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Complete the following table with the correct symbol or name of each element:

Sample Problem 4.1 Names and Symbols of Chemical Elements

a Na (sodium), Group 1A (1), Period 3, is an alkali metal.

b I (iodine), Group 7A (17), Period 5, halogen, is a nonmetal.

c Si (silicon), Group 4A (14), Period 3, is a metalloid.

Study Check 4.2

Strontium is an element that gives a brilliant red color to fireworks

a In what group is strontium found?

b What is the name of this chemical family?

c In what period is strontium found?

d Is strontium a metal, a nonmetal, or a metalloid?

Answer

a Group 2A (2) b. alkaline earth metals c. Period 5 d. metal

Use the periodic table to classify each of the following elements by its group and period, group name (if any),

and as a metal, a nonmetal, or a metalloid:

a Na, important in nerve impulses, regulates blood pressure

b I, needed to produce thyroid hormones

c Si, needed for tendons and ligaments

Sample Problem 4.2 Metals, Nonmetals, and Metalloids

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Is the following statement true or false?

The nucleus occupies a large volume in an atom

Answer

False, most of the volume of the atom is outside the nucleus

Indicate whether each of the following is true or false:

a A proton is heavier than an electron.

b An electron is attracted to a neutron.

c The nucleus contains all the protons and neutrons of an atom.

Sample Problem 4.3 Subatomic Particles

a Zinc (Zn), with an atomic number of 30, has 30 protons.

b The number of neutrons in this atom is found by subtracting number of protons (atomic number) from the

mass number

c Because the zinc atom is neutral, the number of electrons is equal to the number of protons A zinc atom has

Zinc, a micromineral, is needed for metabolic reactions in cells, DNA synthesis, the growth of bones, teeth, and

connective tissue, and the proper functioning of the immune system For an atom of zinc that has a mass number

of 68, determine the following:

a the number of protons b the number of neutrons c the number of electrons

Sample Problem 4.4 Calculating Numbers of Protons, Neutrons,

and Electrons

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

In the atomic symbol, the mass number is shown in the upper left corner of the symbol, and the atomic number is

shown in the lower left corner of the symbol Thus, each isotope of Cr, atomic number 24, has 24 protons The

number of neutrons is found by subtracting the number of protons (24) from the mass number of each isotope

Chromium, a micromineral needed for maintenance of blood sugar levels, has four naturally occurring isotopes:

a b c d

Determine the number of protons and number of neutrons in each of these isotopes

Sample Problem 4.5 Identifying Protons and Neutrons in Isotopes

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C Timberlake

Study Check 4.5

Vanadium is a micromineral needed in the formation of bones and teeth Write the atomic symbol for the single

naturally occurring isotope of vanadium, which has 27 neutrons

Answer

Continued

Sample Problem 4.5 Identifying Protons and Neutrons in Isotopes

Step 1 Multiply the mass of each isotope by its percent abundance divided by 100

Magnesium is a macromineral needed in the

contraction of muscles and metabolic reactions

Using Table 4.7, calculate the atomic mass for

magnesium using the weighted average mass

method

Sample Problem 4.6 Calculating Atomic Mass

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C Timberlake

Step 2 Add the contribution of each isotope to obtain the atomic mass Add the contribution of each isotope to

give the weighted average mass, which is the atomic mass

Atomic mass of Mg = 18.88 amu + 2.531 amu + 2.902 amu

= 24.31 amu (weighted average mass)

Study Check 4.6

There are two naturally occurring isotopes of boron The isotope 105 B has a mass of 10.01 amu with an

abundance of 19.80%, and the isotope 115 B has a mass of 11.01 amu with an abundance of 80.20%

Calculate the atomic mass for boron using the weighted average mass method

Step 1 Draw boxes to represent the occupied orbitals Nitrogen has atomic number 7, which means it has seven

electrons For the orbital diagram, we draw boxes to represent the 1s, 2s, and 2p orbitals.

Step 2 Place a pair of electrons with opposite spins in each filled orbital First, we place a pair of electrons with

opposite spins in both the 1s and 2s orbitals.

Step 3 Place the remaining electrons in the last occupied sublevel in separate orbitals Then we place the three

remaining electrons in three separate 2p orbitals with arrows drawn in the same direction.

Nitrogen is an element that is used in the formation of amino acids, proteins, and nucleic acids Draw the orbital

diagram for nitrogen

Sample Problem 4.7 Drawing Orbital Diagrams

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

a Place two electrons in each orbital, and single electrons in the highest energy level.

Silicon is a micromineral needed for the growth of bones, tendons, and ligaments Draw or write each of the

following for silicon:

a orbital diagram

b abbreviated orbital diagram

c electron configuration

d abbreviated electron configuration

Sample Problem 4.8 Orbital Diagrams and Electron Configurations

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C Timberlake

b Write the symbol for the preceding noble gas followed by the orbitals for the remaining electrons.

c List the sublevels in order of filling and add the number of electrons.

1s22s22p63s23p2 Electron configuration for Si

d Write the symbol for the preceding noble gas followed by the configuration for the remaining electrons.

[Ne]3s23p2 Abbreviated electron configuration for Si

Study Check 4.8

Write the complete and abbreviated electron configurations for sulfur, which is a macromineral in proteins,

vitamin B1, and insulin

Step 1 Locate the element on the periodic table Chlorine (atomic number 17) is in Group 7A (17) and Period 3

Step 2 Write the filled sublevels in order, going across each period

Chlorine is a macromineral that is prevalent in extracellular fluids and stomach acid Use the sublevel blocks on

the periodic table to write the electron configuration for chlorine

Sample Problem 4.9 Using Sublevel Blocks to Write Electron

Configurations

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C Timberlake

Step 3 Complete the configuration by counting the electrons in the last occupied sublevel block Because

chlorine is the fifth element in the 3p block, there are five electrons in the 3p sublevel.

The electron configuration for chlorine (Cl) is: 1s22s22p63s23p5

Study Check 4.9

Use the sublevel blocks on the periodic table to write the electron configuration for magnesium, a macromineral needed

to form bones and required for metabolic reactions

Step 1 Locate the element on the periodic table Selenium is in Period 4 and Group 6A (16)

Step 2 Write the filled sublevels in order, going across each period

Step 3 Complete the configuration by counting the electrons in the last occupied sublevel block Because

selenium is the fourth element in the 4p block, there are four electrons to place in the 4p sublevel.

Selenium is a micromineral used in the immune system and cardiac health Use the sublevel blocks on the periodic

table to write the electron configuration for selenium

Sample Problem 4.10 Using Sublevel Blocks to Write Electron

Configurations

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

The valence electrons are the outermost s and p electrons Although there may be electrons in the d or f sublevels, they

are not valence electrons

a Calcium is in Group 2A (2), Period 4 It has a valence electron configuration of 4s2

b Iodine is in Group 7A (17), Period 5 It has a valence electron configuration of 5s25p5

c Lead is in Group 4A (14), Period 6 It has a valence electron configuration of 6s26p2

Study Check 4.11

What are the group numbers, the periods, and the valence electron configurations for sulfur and strontium?

Answer

Sulfur is in Group 6A (16), Period 3, and has a 3s23p4 valence electron configuration

Strontium is in Group 2A (2), Period 5, and has a 5s2 valence electron configuration

Using the periodic table, write the group number, the period, and the valence electron configuration for the

following:

a calcium b iodine c lead

Sample Problem 4.11 Using Group Numbers

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C Timberlake

Solution

a The Lewis symbol for bromine, which is in Group 7A (17), has seven valence electrons Thus, three pairs of dots

and one single dot are drawn on the sides of the Br symbol

b The Lewis symbol for aluminum, which is in Group 3A (13), has three valence Electrons drawn as single dots on

the sides of the Al symbol

a The F atom has a greater positive charge on the nucleus, which pulls electrons closer, and makes the F atom smaller

than the N atom Atomic size decreases going from left to right across a period

b The Kr atom has a greater positive charge on the nucleus, which pulls electrons closer, and makes the Kr atom

smaller than the K atom Atomic size decreases going from left to right across a period

c The outer electrons in the Ca atom are closer to the nucleus than in the Sr atom, which makes the Ca atom smaller

than the Sr atom Atomic size increases going down a group

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C Timberlake

Solution

a Na In Na, an electron is removed from an energy level closer to the nucleus, which requires a higher ionization

energy for Na compared to K

b Cl The increased nuclear charge of Cl increases the attraction for the valence electrons, which requires a higher

ionization energy for Cl compared to Mg

c F The increased nuclear charge of F increases the attraction for the valence electrons, which requires a higher

ionization energy for F compared to C or N

Study Check 4.14

Arrange Sn, Sr, and I in order of increasing ionization energy

Answer

Ionization energy increases going from left to right across a period: Sr, Sn, I

Indicate the element in each group that has the higher ionization energy and explain your choice

a K or Na b Mg or Cl c F, N, or C

Sample Problem 4.14 Ionization Energy