Chapter 3 Atoms and Elements

Chapter 3 Atoms and Elements
3.1 Elements and Symbols

Elements Elements are pure substances that cannot be separated into simpler substances by ordinary laboratory processes the building blocks of matter listed on the inside front cover of this text

Some Elements and Their Names
Names come from: planets mythological figures minerals colors geographic locations famous people

Chemical Symbols Chemical Symbols represent name of element
consist of one to two letters and start with capital 1-Letter Symbols Letter Symbols C carbon Co cobalt N nitrogen Ca calcium F fluorine Al aluminum O oxygen Mg magnesium

Chemical Symbols from Latin Names
Ag silver, from argentum Au gold, from aurum

Learning Check Write the correct chemical symbols for each of the following elements: A. iodine B. iron C. magnesium D. zinc E. nitrogen

Solution Write the symbols for each of the following elements:
A. iodine = I B. iron = Fe C. magnesium = Mg D. zinc = Zn E. nitrogen = N

Learning Check Give the names of the elements with the following symbols: A. P B. Al C. Mn D. H E. K

Solution Give the names of the elements with the following symbols: A. P = phosphorus B. Al = aluminum C. Mn = manganese D. H = hydrogen E. K = potassium

3.2 The Periodic Table

Groups and Periods On the periodic table,
elements are arranged according to similar properties groups contain elements with similar properties in vertical columns periods are horizontal rows of elements

Groups and Periods

Periodic Table of Elements

Group Numbers Group numbers
use the letter A for representative elements (Groups 1A–8A) use the letter B for transition elements (Groups 3B–12B)

Classification of Groups

Alkali Metals Group 1A, the alkali metals, includes lithium, sodium, potassium, rubidium, and cesium.

Halogens Group 7A, the halogens, includes chlorine, bromine, and iodine.

Learning Check Identify the element described by the following:
1. Group 7A, Period 4 A. Br B. Cl C. Mn 2. Group 2A, Period 3 A. beryllium B. boron C. magnesium 3. Group 5A, Period 2 A. phosphorus B. arsenic C. nitrogen

Solution Identify the element described by the following:
1. Group 7A, Period 4 A. Br 2. Group 2A, Period 3 C. magnesium 3. Group 5A, Period 2 C. nitrogen

Metals, Nonmetals, and Metalloids
The heavy zigzag line separates metals and nonmetals. Metals are located to the left. Nonmetals are located to the right. Metalloids are located along the heavy zigzag line between the metals and nonmetals.

Metals, Nonmetals, and Metalloids and Periodic Table

Properties of Metals, Nonmetals, and Metalloids
are shiny and ductile are good conductors of heat and electricity Nonmetals are dull, brittle, and poor conductors are good insulators Metalloids are better conductors than nonmetals, but not as good as metals are used as semiconductors and insulators

Comparing a Metal, Nonmetal, and Metalloid

Learning Check Identify each of the following elements as a metal, nonmetal, or metalloid. A. sodium B. chlorine C. silicon D. iron E. carbon

Solution Identify each of the following elements as metal, nonmetal, or metalloid. A. sodium metal B. chlorine nonmetal C. silicon metalloid D. iron metal E. carbon nonmetal

Learning Check List all of the elements that match the description A. Metals in Group 4A Sn, Pb, C, Si, Ge B. Nonmetals in Group 5A As, Sb, Bi, N, P, As, Sb C. Metalloids in Group 4A C, Si, Ge, Sn, Pb

Solution List all of the elements that match the description A. Metals in Group 4A Sn, Pb B. Nonmetals in Group 5A N, P C. Metalloids in Group 4A Si, Ge

Dalton's Atomic Theory In Dalton's atomic theory, atoms
are tiny particles of matter of an element are similar to each other and different from other elements of two or more different elements combine to form compounds are rearranged to form new combinations in a chemical reaction Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Subatomic Particles Electrical Charges
Atoms contain subatomic particles. Protons have a positive (+) charge. Electrons have a negative (–) charge. Neutrons are neutral. Like charges repel and unlike charges attract. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Rutherford's Gold Foil Experiment
In Rutherford’s gold foil experiment, positively charged particles were aimed at atoms of gold mostly went straight through the atoms were deflected only occasionally Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Rutherford's Gold Foil Experiment
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Structure of the Atom An atom consists of
a nucleus that contains protons and neutrons electrons in a large, empty space around the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Mass of the Atom Atomic mass unit
1 atomic mass unit (amu) has a mass equal to 1/12 of the mass of the carbon-12 atom. a proton has a mass of about 1 (1.007) amu. a neutron has a mass of about 1 (1.008) amu. an electron has a very small mass, amu. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Subatomic Particles in the Atom

Learning Check Which of the following subatomic particles fits each of the descriptions below: proton, neutrons, or electrons A. found outside the nucleus B. has a positive charge C. has mass but no charge Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Which of the following subatomic particles fits each of the descriptions below: proton, neutrons, or electrons A. found outside the nucleus electrons B. has a positive charge protons C. has mass but no charge neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

11 Na Atomic Number Atomic Number Symbol The atomic number
is specific for each element is the same for all atoms of an element is equal to the number of protons in an atom appears above the symbol of an element in the Periodic Table Atomic Number Symbol 11 Na Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Number = Protons in Atom
For example, atomic number = number of protons: Atomic number H is 1; every H atom has one proton Atomic number of C is 6; every C atom has six protons Atomic number of Cu is 29; every Cu atom has 29 protons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Number = Protons in Atom

Atoms Are Neutral For neutral atoms, the net charge is zero.
number of protons = number of electrons Aluminum has 13 protons and 13 electrons. The net (overall) charge is zero. 13 protons (13+) electrons (13–) = 0 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Use the periodic table to fill in the atomic number, number of protons, and number of electrons for each of the following elements: Element Atomic Number Protons Electrons N Zn S Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Use the periodic table to fill in the atomic number, number of protons, and number of electrons for each of the following elements: Element Atomic Number Protons Electrons N 7 Zn 30 S 16 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Mass Number The mass number
represents the number of particles in the nucleus is equal to the number of protons + the number of neutrons is always a whole number does not appear in the periodic table Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Composition of Some Atoms of Different Elements

Study Tips: Protons and Neutrons
Number of protons = atomic number Number of protons + neutrons = mass number Number of neutrons = mass number – atomic number Note: Mass number is given for specific isotopes only. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check An atom of lead (Pb) has a mass number of 207.
A. How many protons are in the nucleus? B. How many neutrons are in the nucleus? C. How many electrons are in the atom? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution An atom of lead (Pb) has a mass number of 207.
A. How many protons are in the nucleus? atomic number = 82; number protons = 82 B. How many neutrons are in the nucleus? mass number – number protons = number neutrons 207 – 82 = 125 neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution An atom of lead (Pb) has a mass number of 207.
C. How many electrons are in the atom? An atom is neutral, which means that the number of electrons is equal to the number of protons. An atom of Pb has 82 protons and 82 electrons. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Isotopes Isotopes are atoms of the same element
have different mass numbers have same number of protons but different numbers of neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Symbols and Subatomic Particles
Examples of number of subatomic particles for atoms: Atomic symbol O P Zn 8 p+ 15 p p+ 8 n 16 n n 8 e- 15 e e- Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Symbols for Isotopes of Magnesium
Mass Numbers Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons neutrons electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons 6 neutrons 7 8 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Write the atomic symbols for atoms with the following subatomic particles: A. 8 protons neutrons electrons B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Write the atomic symbols for atoms with the following subatomic particles: A. 8 protons neutrons electrons B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check 1. Which of the pairs are isotopes of the same element?
2. In which of the pairs do both atoms have 8 neutrons? A. B. C. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Mass Atomic mass is the
weighted average of all naturally occurring isotopes of that element number on the periodic table below the chemical symbol with two decimal places Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Calculating Atomic Mass
To calculate atomic mass, use an experimental percent abundance of each isotope of the element multiply the percent abundance by the atomic mass of that isotope sum the total mass of each isotope Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

To calculate atomic mass of Cl, use experimental data for both isotopes of Cl: Isotope atomic mass x % abundance 35Cl amu x = amu 100 37Cl amu x = amu Atomic mass of Cl = amu Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

The Atomic Mass of Some Elements

Learning Check Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is amu. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is amu. 6Li and 7Li Since the total atomic mass of 7Li is closer to 7, the mass number of 7Li, the most prevalent isotope is 7Li. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Gallium is an element found in lasers used in compact disc players. In a sample of gallium, there is 60.10% of 69Ga (atomic mass ) atoms and 39.90% of 71Ga (atomic mass ) atoms. What is the atomic mass of gallium? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution 69Ga amu x = amu (from 69Ga) Ga amu x = amu (from 71Ga) Atomic mass Ga = amu 31 Ga 69.72 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Isotopes Isotopes are atoms of the same element
have different mass numbers have same number of protons but different numbers of neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Symbols and Subatomic Particles
Examples of number of subatomic particles for atoms: Atomic symbol O P Zn 8 p+ 15 p p+ 8 n 16 n n 8 e- 15 e e- Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons neutrons electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons 6 neutrons 7 8 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Write the atomic symbols for atoms with the following subatomic particles: A. 8 protons neutrons electrons B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Write the atomic symbols for atoms with the following subatomic particles: A. 8 protons neutrons electrons B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Mass Atomic mass is the
weighted average of all naturally occurring isotopes of that element number on the periodic table below the chemical symbol with two decimal places Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

To calculate atomic mass, use an experimental percent abundance of each isotope of the element multiply the percent abundance by the atomic mass of that isotope sum the total mass of each isotope Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

To calculate atomic mass of Cl, use experimental data for both isotopes of Cl: Isotope atomic mass x % abundance 35Cl amu x = amu 100 37Cl amu x = amu Atomic mass of Cl = amu Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

The Atomic Mass of Some Elements

Learning Check Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is amu. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is amu. 6Li and 7Li Since the total atomic mass of 7Li is closer to 7, the mass number of 7Li, the most prevalent isotope is 7Li. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Gallium is an element found in lasers used in compact disc players. In a sample of gallium, there is 60.10% of 69Ga (atomic mass ) atoms and 39.90% of 71Ga (atomic mass ) atoms. What is the atomic mass of gallium? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution 69Ga amu x = amu (from 69Ga) Ga amu x = amu (from 71Ga) Atomic mass Ga = amu 31 Ga 69.72 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electromagnetic Spectrum
The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Elements Have a Unique Atomic Spectrum
When light from an element that is heated passes through a prism, it separates into a unique set of distinct lines of color called an atomic spectrum. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Energy Levels
are assigned numbers n = 1, 2, 3, 4, and so on increase in energy as the value of n increases are like the rungs of a ladder, with the lower energy levels nearer the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Energy Levels Energy levels have a maximum number of electrons equal to 2n2. Energy level Maximum number of electrons n = 1 2(1)2 = 2(1) = 2 n = 2 2(2)2 = 2(4) = 8 n = 3 2(3)2 = 2(9) = 18 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Changes in Electron Energy Level
Electrons move to a higher energy level when it absorbs energy. When electrons fall back to a lower energy level, light is emitted. The energy emitted or absorbed is equal to the differences between the two energy levels. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements in Period 1
H 1 electron in 1st energy level. He 2 electrons in 1st energy level. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements Beyond 20
Energy Level 1st 2nd rd th th 6th 7th Number of Electrons Electron arrangements are written as: O = 2,6 P = 2,8,5 Ca = 2,8,8,2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Write the electron arrangement for the following elements: C Si O N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Write the electron arrangement for the following elements:
Si = 2,8,4 O = 2,6 N = 2,5 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Group Number and Valence Electrons
For representative elements in Groups 1A–8A, chemical properties are due to the number of valence electrons. Valence electrons are the number of electrons in the outermost energy level. The group number gives the number of valence electrons for the representative elements. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Group Number and Valence Electrons
Group Number # Valence Electrons 1A 1 2A 2 3A 3 4A 4 5A 5 6A 6 7A 7 8A 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron-Dot Symbols Electron-dot symbols
are also known as Lewis structures represent the valence electrons as dots placed on sides of symbol For example, Al = 2,8,3 Three valence electrons are represented as dots: Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron-Dot Symbol for Mg
Possible electron-dot symbols for magnesium, with the electron arrangement of 2,8,2, include 2 valence electrons, represented as dots can be drawn in more than one way Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron-Dot Symbol for Mg

Electron-Dot Symbols for Selected Elements

Learning Check Write the electron-dot symbol for each of the following elements: Cl, C, N. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Write the electron-dot symbol for each of the following elements: Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Atomic Size Atomic size
is determined by the atom’s atomic radius, the distance between nucleus and outermost electrons increases for representative elements from top to bottom of the periodic table decreases within a period due to increased number of protons in nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Ionization Energy Ionization energy
is the energy required to remove one of the outermost electrons from an atom Na(g) + energy (ionization)  Na+(g) + e− decreases down a group, increases across a period from left to right Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Metallic Character An element with metallic character is one that loses electrons easily. Metallic character is more prevalent in metals on left side of periodic table is less for nonmetals on right side of periodic table that do not lose electrons easily Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Summary of Trends in Periodic Table

Learning Check Given the following elements: C N Cl
Which is the largest atom? Which has the highest ionization energy? Which belongs to Group 5A? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Given the following elements: C N Cl
Which is the largest atom? C Which has the highest ionization energy? Cl Which belongs to Group 5A? N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Chapter 3 Atoms and Elements

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