Transcript Sample Problem 3.1 Writing Chemical Symbols What are the chemical symbols for the following elements? a.

Sample Problem 3.1 Writing Chemical Symbols
What are the chemical symbols for the following elements?
a. nickel
b. nitrogen
c. neon
Solution
a. Ni
b. N
c. Ne
Study Check 3.1
What are the chemical symbols for the elements silicon, sulfur, and silver?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.2 Names and Symbols of Chemical Elements
Give the name of the element that corresponds to each of the following chemical symbols:
a. Zn
b. K
c. H
d. Fe
Solution
a. zinc
b. potassium
c. hydrogen
d. iron
Study Check 3.2
What are the names of the elements with the chemical symbols Mg, Al, and F?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.3 Group and Period Numbers of Some Elements
Give the period and group for each of the following elements and identify as a representative or transition element:
a. iodine
b. manganese
c. barium
d. gold
Solution
a. Iodine (I), Period 5, Group 7A (17), is a representative element.
b. Manganese (Mn), Period 4, Group 7B (7), is a transition element.
c. Barium (Ba), Period 6, Group 2A (2), is a representative element.
d. Gold (Au), Period 6, Group 1B (11), is a transition element.
Study Check 3.3
Strontium is an element that gives a brilliant red
color to fireworks.
a. In what group is strontium found?
b. In what chemical family is strontium found?
c. In what period is strontium found?
d. What are the name and symbol of the element in Period 3 that is in the same group as strontium?
e. What alkali metal, halogen, and noble gas are in the same period as strontium?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.4 Metals, Nonmetals or Metalloids
Use the periodic table to classify each of the following elements by its group and period, group name (if any), and
as a metal, nonmetal, or metalloid:
a. Na
b. I
c. B
Solution
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. B (boron), Group 3A (13), Period 2, is a metalloid.
Study Check 3.4
Give the name and symbol of the following elements:
a. Group 5A (15), Period 4
b. A noble gas in Period 3
c. A metalloid in Period 3
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.5 Identifying Subatomic Particles
Identify the subatomic particle that has the following characteristics:
a. no charge
b. a mass of 0.000 55 amu
c. a mass about the same as a neutron
Solution
a. neutron
b. electron
c. proton
Study Check 3.5
Is the following statement true or false?
The nucleus occupies a large volume in an atom.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.6 Using Atomic Numbers to Find the Number
of Protons and Electrons
Using the periodic table in Figure 3.1, state the atomic number, number of protons, and number of electrons for an
atom of each of the following elements:
a. nitrogen
b. magnesium
c. bromine
Solution
a. atomic number 7; 7 protons and 7 electrons
b. atomic number 12; 12 protons and 12 electrons
c. atomic number 35; 35 protons and 35 electrons
Study Check 3.6
Consider an atom that has 79 electrons.
a. How many protons are in its nucleus?
b. What is its atomic number?
c. What is its name, and what is its symbol?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.7 Calculating Numbers of Protons, Neutrons
and Electrons
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
Solution
a. Zinc (Zn), with an atomic number of 30, has 30 protons.
b. The number of neutrons in this atom is found by subtracting the atomic number from the mass number.
Mass number – atomic number = number of neutrons
68
–
30
=
38
c. Because the zinc atom is neutral, the number of electrons is equal to the number of protons. A zinc atom
has 30 electrons.
Study Check 3.7
How many neutrons are in the nucleus of a bromine atom that has a mass number of 80?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.8 Identifying Protons and Neutrons in Isotopes
State the number of protons and neutrons for each of the following isotopes of neon (Ne):
a.
b.
c.
Solution
The atomic number of Ne is 10, which means that the nucleus of each isotope has 10 protons. The number
of neutrons in each isotope is found by subtracting the atomic number (10) from each of their mass
numbers.
a. 10 protons; 10 neutrons (20 – 10)
b. 10 protons; 11 neutrons (21 – 10)
c. 10 protons; 12 neutrons (22 – 10)
Study Check 3.8
Write an atomic symbol for each of the following:
a. a nitrogen atom with 8 neutrons
b. an atom with 20 protons and 22 neutrons
c. an atom with mass number 27 and 14 neutrons
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.9 Calculating Atomic Mass
Using Table 3.7, calculate the atomic mass for magnesium using the weighted average mass method.
Solution
10
5
11
5
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.9 Calculating Atomic Mass
Continued
Study Check 3.9
There are two naturally occurring isotopes of boron. The isotope 105B has a mass of 10.01 amu with an
abundance of 19.80%, and the isotope 115B has a mass of 11.01 amu with an abundance of 80.20%. What is
the atomic mass of boron?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.10 Writing Electron Arrangments
Write the electron arrangement for each of the following:
a. oxygen
b. chlorine
Solution
a. Oxygen with atomic number 8, has eight electrons, which are arranged with two electrons in energy level
1 and six electrons in energy level 2.
2,6
b. Chlorine with atomic number 17, has 17 electrons, which are arranged with 2 electrons in energy level 1,
8 electrons in energy level 2, and 7 electrons in energy level 3.
2,8,7
Study Check 3.10
What element has an electron arrangement of 2,8,5?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.11 Using Group Numbers
Using the periodic table, write the group number and the number of valence electrons for each of the following
elements:
a. cesium
b. iodine
Solution
a. Cesium (Cs) is in Group 1A (1); cesium has one valence electron.
b. Iodine (I) is in Group 7A (17); iodine has seven valence electrons.
Study Check 3.11
What is the group number of elements with atoms that have five valence electrons?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.12 Writing Electron-Dot Symbols
Write the electron-dot symbol for each of the following:
a. bromine
b. aluminum
Solution
a. Because the group number for bromine is 7A (17), bromine has seven valence electrons, which are drawn
as seven dots, three pairs and one single dot, around the symbol Br.
b. Aluminum, in Group 3A (13), has three valence electrons, which are shown as three single dots around
the symbol Al.
Study Check 3.12
What is the electron-dot symbol for phosphorus?
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.
Sample Problem 3.13 Ionization Energy
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
Solution
a. Na. In Na, the valence electron is closer to the nucleus.
b. Cl. Attraction for the valence electrons increases going from left to right across a period.
c. F. Attraction for the valence electrons increases going from left to right across a period.
Study Check 3.13
Arrange Sn, Sr, and I in order of increasing ionization energy.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, 11th Edition
Karen C. Timberlake
© 2012 Pearson Education, Inc.